Remove invalid combinations from tox

[adamchainz]

Follow-up to #248, removing Python 3.11 from Django 3.2 and 4.0, since they don't support it.

[codecov[bot]]

Codecov Report

Merging #249 (78a85d5) into master (331b406) will not change coverage. The diff coverage is n/a.

@@           Coverage Diff           @@
##           master     #249   +/-   ##
=======================================
  Coverage   93.83%   93.83%           
=======================================
  Files          11       11           
  Lines         535      535           
  Branches       87       87           
=======================================
  Hits          502      502           
  Misses         21       21           
  Partials       12       12           

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[claudep]

:+1: