Bump Python versions to 3.9 and 3.11 in GitHub CI workflow

[oskooi]

The Python 3.7 build of the CI is failing due to a package conflict involving JAX. This is because the JAX PyPI package recently released version 0.4.20 requires Python >= 3.9.

Rather than pin the JAX PyPI package to an older version which would likely create package conflicts elsewhere, this PR updates the GitHub CI workflow to use the newer Python versions 3.9 and 3.11.

[codecov-commenter]

Codecov Report

Merging #2702 (3db7629) into master (eee9972) will increase coverage by 0.37%. Report is 1 commits behind head on master. The diff coverage is n/a.

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@@            Coverage Diff             @@
##           master    #2702      +/-   ##
==========================================
+ Coverage   73.69%   74.06%   +0.37%     
==========================================
  Files          18       18              
  Lines        5318     5394      +76     
==========================================
+ Hits         3919     3995      +76     
  Misses       1399     1399              

see 6 files with indirect coverage changes