Hello,

Slack has released updates to its library and we can start using it for it. 

We especially like one change.

> slack_sdk has no required dependencies. This means aiohttp is no longer automatically resolved.

I've looked through the documentation and it doesn't look like a difficult task, but I think it's still worth testing.
More info: https://slack.dev/python-slack-sdk/v3-migration/index.html#from-slackclient-2-x

Best regards,
Kamil Breguła
docs/conf.py
else:
    exclude_patterns.extend(
        _get_rst_filepath_from_path(f) for f in glob.glob(f"{PACKAGE_DIR}/**/example_dags/**/*.py")
    )
templates_path = ['templates']
keep_warnings = True
html_theme = 'sphinx_airflow_theme'
if PACKAGE_NAME == 'apache-airflow':
    html_title = "Airflow Documentation"
else:
    html_title = f"{PACKAGE_NAME} Documentation"
html_short_title = ""
html_favicon = "../airflow/www/static/pin_32.png"
if PACKAGE_NAME == 'apache-airflow':
    html_static_path = ['apache-airflow/static']
else:
    html_static_path = []
if PACKAGE_NAME == 'apache-airflow':
    html_js_files = ['jira-links.js']
else:
    html_js_files = []
html_sidebars = {
    '**': [
        'version-selector.html',
        'searchbox.html',
        'globaltoc.html',
    ]
    if FOR_PRODUCTION
    else [
        'searchbox.html',