When you've never built `helm-chart` documentation package locally. the intersphinx repository is missing for it and it cannot be downloaded as the helm-chart package is never published as package (I guess) . 

This fails for example our command to build provider's documentation when you release providers:

```
cd "${AIRFLOW_REPO_ROOT}"
./breeze build-docs -- \
  --for-production \
  --package-filter apache-airflow-providers \
  --package-filter 'apache-airflow-providers-*'
```

Adding `--package-filter 'helm-chart'` helps, but it also builds the helm-chart documentation which is undesired in this case (and it causes the docs-building for most providers to fail the first pass, until the `helm-chart` documentation is built

Possibly there is a way to get rid of that dependency ? 

The error you get:

```
apache-airflow-providers                                     Traceback (most recent call last):
apache-airflow-providers                                       File "/usr/local/lib/python3.6/site-packages/sphinx/cmd/build.py", line 279, in build_main
apache-airflow-providers                                         args.tags, args.verbosity, args.jobs, args.keep_going)
apache-airflow-providers                                       File "/usr/local/lib/python3.6/site-packages/sphinx/application.py", line 278, in __init__
apache-airflow-providers                                         self._init_builder()
apache-airflow-providers                                       File "/usr/local/lib/python3.6/site-packages/sphinx/application.py", line 337, in _init_builder
apache-airflow-providers                                         self.events.emit('builder-inited')
apache-airflow-providers                                       File "/usr/local/lib/python3.6/site-packages/sphinx/events.py", line 110, in emit
apache-airflow-providers                                         results.append(listener.handler(self.app, *args))
apache-airflow-providers                                       File "/usr/local/lib/python3.6/site-packages/sphinx/ext/intersphinx.py", line 238, in load_mappings
apache-airflow-providers                                         updated = 
apache-airflow-providers                                       File "/usr/local/lib/python3.6/site-packages/sphinx/ext/intersphinx.py", line 238, in <listcomp>
apache-airflow-providers                                         updated = 
apache-airflow-providers                                       File "/usr/local/lib/python3.6/concurrent/futures/_base.py", line 425, in result
apache-airflow-providers                                         return self.__get_result()
apache-airflow-providers                                       File "/usr/local/lib/python3.6/concurrent/futures/_base.py", line 384, in __get_result
apache-airflow-providers                                         raise self._exception
apache-airflow-providers                                       File "/usr/local/lib/python3.6/concurrent/futures/thread.py", line 56, in run
apache-airflow-providers                                         result = self.fn(*self.args, **self.kwargs)
apache-airflow-providers                                       File "/usr/local/lib/python3.6/site-packages/sphinx/ext/intersphinx.py", line 224, in fetch_inventory_group
apache-airflow-providers                                         "with the following issues:") + "\n" + issues)
apache-airflow-providers                                       File "/usr/local/lib/python3.6/logging/__init__.py", line 1642, in warning
apache-airflow-providers                                         self.log(WARNING, msg, *args, **kwargs)
apache-airflow-providers                                       File "/usr/local/lib/python3.6/site-packages/sphinx/util/logging.py", line 126, in log
apache-airflow-providers                                         super().log(level, msg, *args, **kwargs)
apache-airflow-providers                                       File "/usr/local/lib/python3.6/logging/__init__.py", line 1674, in log
apache-airflow-providers                                         self.logger.log(level, msg, *args, **kwargs)
apache-airflow-providers                                       File "/usr/local/lib/python3.6/logging/__init__.py", line 1374, in log
apache-airflow-providers                                         self._log(level, msg, args, **kwargs)
apache-airflow-providers                                       File "/usr/local/lib/python3.6/logging/__init__.py", line 1444, in _log
apache-airflow-providers                                         self.handle(record)
apache-airflow-providers                                       File "/usr/local/lib/python3.6/logging/__init__.py", line 1454, in handle
apache-airflow-providers                                         self.callHandlers(record)
apache-airflow-providers                                       File "/usr/local/lib/python3.6/logging/__init__.py", line 1516, in callHandlers
apache-airflow-providers                                         hdlr.handle(record)
apache-airflow-providers                                       File "/usr/local/lib/python3.6/logging/__init__.py", line 861, in handle
apache-airflow-providers                                         rv = self.filter(record)
apache-airflow-providers                                       File "/usr/local/lib/python3.6/logging/__init__.py", line 720, in filter
apache-airflow-providers                                         result = f.filter(record)
apache-airflow-providers                                       File "/usr/local/lib/python3.6/site-packages/sphinx/util/logging.py", line 422, in filter
apache-airflow-providers                                         raise exc
apache-airflow-providers                                     sphinx.errors.SphinxWarning: failed to reach any of the inventories with the following issues:
apache-airflow-providers                                     intersphinx inventory '/opt/airflow/docs/_inventory_cache/helm-chart/objects.inv' not fetchable due to <class 
'FileNotFoundError'>: [Errno 2] No such file or directory: '/opt/airflow/docs/_inventory_cache/helm-chart/objects.inv'
apache-airflow-providers                                     
apache-airflow-providers                                     [91mWarning, treated as error:[39;49;00m
apache-airflow-providers                                     failed to reach any of the inventories with the following issues:
apache-airflow-providers                                     intersphinx inventory '/opt/airflow/docs/_inventory_cache/helm-chart/objects.inv' not fetchable due to <class 
'FileNotFoundError'>: [Errno 2] No such file or directory: '/opt/airflow/docs/_inventory_cache/helm-chart/objects.inv'

```
docs/exts/docs_build/fetch_inventories.py
ROOT_DIR = os.path.abspath(os.path.join(CURRENT_DIR, os.pardir, os.pardir, os.pardir))
DOCS_DIR = os.path.join(ROOT_DIR, 'docs')
CACHE_DIR = os.path.join(DOCS_DIR, '_inventory_cache')
EXPIRATION_DATE_PATH = os.path.join(DOCS_DIR, '_inventory_cache', "expiration-date")
S3_DOC_URL = "http://apache-airflow-docs.s3-website.eu-central-1.amazonaws.com"
S3_DOC_URL_VERSIONED = S3_DOC_URL + "/docs/{package_name}/latest/objects.inv"
S3_DOC_URL_NON_VERSIONED = S3_DOC_URL + "/docs/{package_name}/objects.inv"
def _fetch_file(session: requests.Session, package_name: str, url: str, path: str) -> Tuple[str, bool]:
    """
    Download a file and returns status information as a tuple with package
    name and success status(bool value).
    """
    try:
        response = session.get(url, allow_redirects=True, stream=True)
    except (requests.RequestException, urllib3.exceptions.HTTPError):
        print(f"Failed to fetch inventory: {url}")
        traceback.print_exc(file=sys.stderr)
        return package_name, False
    if not response.ok:
        print(f"Failed to fetch inventory: {url}")
        print(f"Failed with status: {response.status_code}", file=sys.stderr)
        return package_name, False
    os.makedirs(os.path.dirname(path), exist_ok=True)
    with open(path, 'wb') as f:
        response.raw.decode_content = True
        shutil.copyfileobj(response.raw, f)
    print(f"Fetched inventory: {url}")
    return package_name, True
def _is_outdated(path: str):
    if not os.path.exists(path):