feat: drop django 2.2, 3.0, and 3.1 support

[dopry]

Drop support for EOL Django versions 2.2, 3.0, and 3.1

Motivation and Context

As an open-source team, we don't have the resources to maintain compatibility with end-of-life code. Consumers who need to work with older versions of Django can use older releases.

Checklist:

• [X] My change requires a change to the documentation.
• [X] I have updated the documentation accordingly.

[codecov[bot]]

Codecov Report

Merging #497 (4bd592c) into master (4bd592c) will not change coverage. The diff coverage is n/a.

:exclamation: Current head 4bd592c differs from pull request most recent head b679c6b. Consider uploading reports for the commit b679c6b to get more accurate results

@@           Coverage Diff           @@
##           master     #497   +/-   ##
=======================================
  Coverage   98.53%   98.53%           
=======================================
  Files          60       60           
  Lines        2659     2659           
  Branches      278      278           
=======================================
  Hits         2620     2620           
  Misses         24       24           
  Partials       15       15           

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[claudep]

As a release might come soon, I would suggest to wait a bit and merge this just after the release.

[claudep]

I don't trust codecov results for a long time now... don't bother.

[claudep]

@moggers87 We need your review to go forward as you requested changes.