Fixed a few PEP8 errors in settings doc.
Fixed #22966 -- Clarified which release notes appear for each doc version.

Thanks haimunt at yahoo.com for the suggestion.
Fixed #22942 -- Noted that __init__.py files are required for management command detection.

Thanks Diego Cerdán for the suggestion.
Fixed #22909 -- Removed camelCasing in some tests.

Thanks brylie.
Fixed flake8 errors.
Removed unnecessary directory in dispatch tests.