Update supported Python and Django versions

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Comparison is base (8c16b57) 90.14% compared to head (c848e33) 90.14%. Report is 1 commits behind head on master.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #449 +/- ## ======================================= Coverage 90.14% 90.14% ======================================= Files 6 6 Lines 284 284 Branches 50 51 +1 ======================================= Hits 256 256 Misses 12 12 Partials 16 16 ```

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