gha: updating python versions

[andrsd]

• dropping 3.9
• adding 3.13

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 88.94%. Comparing base (70bf9c4) to head (fc6d86e).
⚠️ Report is 2 commits behind head on main.
✅ All tests successful. No failed tests found.

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #89      +/-   ##
==========================================
- Coverage   89.04%   88.94%   -0.10%     
==========================================
  Files          62       62              
  Lines        1004     1004              
==========================================
- Hits          894      893       -1     
- Misses        110      111       +1     

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