Also deprecate Python 3.8

[lunkwill42]

Our deprecation of Python 3.7 is a de-facto deprecation also of Python 3.8, since we will only explicitly target that and newer versions. The notes and changelogs should be more explicit about this.

[codecov[bot]]

Codecov Report

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

Project coverage is 60.25%. Comparing base (513c0e4) to head (e12a6fd).

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #2919 +/- ## ======================================= Coverage 60.25% 60.25% ======================================= Files 602 602 Lines 44084 44084 ======================================= Hits 26565 26565 Misses 17519 17519 ```

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[github-actions[bot]]

Test results

   12 files     12 suites   11m 53s :stopwatch: 3 325 tests 3 325 :white_check_mark: 0 :zzz: 0 :x: 9 450 runs  9 450 :white_check_mark: 0 :zzz: 0 :x:

Results for commit e12a6fd2.

:recycle: This comment has been updated with latest results.