### Summary

Running `ansible-doc -l` generates 430 deprecation warnings on stderr before printing anything to stdout.
```
[DEPRECATION WARNING]: amazon.aws.aws_az_facts has been deprecated.
aws_az_facts was renamed in Ansible 2.9 to aws_az_info. Please update your
tasks. This feature will be removed from amazon.aws in a release after
2022-06-01. Deprecation warnings can be disabled by setting
deprecation_warnings=False in ansible.cfg.

[DEPRECATION WARNING]: amazon.aws.aws_caller_facts has been deprecated.
aws_caller_facts was renamed in Ansible 2.9 to aws_caller_info. Please update
your tasks. This feature will be removed from amazon.aws in a release after
2021-12-01. Deprecation warnings can be disabled by setting
deprecation_warnings=False in ansible.cfg.
...
```

### Issue Type

Bug Report

### Component Name

ansible-doc

### Ansible Version

```console
$ ansible-doc --version

ansible-doc 2.10.6
  config file = None
  configured module search path = [u'/home/charleshowes/.ansible/plugins/modules', u'/usr/share/ansible/plugins/modules']
  ansible python module location = /usr/local/lib/python2.7/dist-packages/ansible
  executable location = /usr/local/bin/ansible-doc
  python version = 2.7.17 (default, Sep 30 2020, 13:38:04) [GCC 7.5.0]
```


### Configuration

```console
$ ansible-config dump --only-changed
(no output)
```


### OS / Environment

Ubuntu 18.04

### Steps to Reproduce

<!--- Paste example playbooks or commands between quotes below -->
```shell (paste below)
ansible-doc -l
```


### Expected Results

I expected to see a list of available plugins, and was shocked to have pages and pages of warnings.

### Actual Results

```console
$ ansible-doc -l 2>&1 | head

[DEPRECATION WARNING]: amazon.aws.aws_az_facts has been deprecated. 
aws_az_facts was renamed in Ansible 2.9 to aws_az_info. Please update your 
tasks. This feature will be removed from amazon.aws in a release after 
2022-06-01. Deprecation warnings can be disabled by setting 
deprecation_warnings=False in ansible.cfg.
[DEPRECATION WARNING]: amazon.aws.aws_caller_facts has been deprecated. 
aws_caller_facts was renamed in Ansible 2.9 to aws_caller_info. Please update 
your tasks. This feature will be removed from amazon.aws in a release after 
2021-12-01. Deprecation warnings can be disabled by setting 
deprecation_warnings=False in ansible.cfg.

$ ansible-doc -l 2>&1 | grep -c 'DEPRECATION WARNING'

430
```


### Code of Conduct

- [X] I agree to follow the Ansible Code of Conduct
''' Return a list of paths to search for plugins in '''
        paths_with_context = self._get_paths_with_context(subdirs=subdirs)
        return [path_with_context.path for path_with_context in paths_with_context]
    def _load_config_defs(self, name, module, path):
        ''' Reads plugin docs to find configuration setting definitions, to push to config manager for later use '''
        
        if self.class_name:
            type_name = get_plugin_class(self.class_name)
            
            if type_name in C.CONFIGURABLE_PLUGINS:
                dstring = AnsibleLoader(getattr(module, 'DOCUMENTATION', ''), file_name=path).get_single_data()
                if dstring:
                    add_fragments(dstring, path, fragment_loader=fragment_loader, is_module=(type_name == 'module'))
                if dstring and 'options' in dstring and isinstance(dstring['options'], dict):
                    C.config.initialize_plugin_configuration_definitions(type_name, name, dstring['options'])
                    display.debug('Loaded config def from plugin (%s/%s)' % (type_name, name))
    def add_directory(self, directory, with_subdir=False):
        ''' Adds an additional directory to the search path '''
        directory = os.path.realpath(directory)
        if directory is not None:
            if with_subdir:
                directory = os.path.join(directory, self.subdir)
            if directory not in self._extra_dirs:
                
                self._extra_dirs.append(directory)
                self._clear_caches()
                display.debug('Added %s to loader search path' % (directory))
    def _query_collection_routing_meta(self, acr, plugin_type, extension=None):