Enhancement: Update supported Python versions

[RHammond2]

This PR updates Python support from 3.8 through 3.11 to 3.9 through 3.12. Additionally, the note stemming from early 3.11 support has been removed as pip's resolver is much better than when the warning was written.

The only thing stopping OpenOA from supporting 3.13 is pyGAM, which has not had a new version release since February 2024. This library does not seem to have an immediate replacement, so further work must be done if pyGAM becomes deprecated.

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 69.92%. Comparing base (a53308e) to head (b1ed52d).
Report is 17 commits behind head on develop.

Additional details and impacted files

@@             Coverage Diff             @@
##           develop     #309      +/-   ##
===========================================
- Coverage    72.49%   69.92%   -2.58%     
===========================================
  Files           29       29              
  Lines         3690     3840     +150     
  Branches       796      573     -223     
===========================================
+ Hits          2675     2685      +10     
- Misses         826      967     +141     
+ Partials       189      188       -1     

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[ejsimley]

Thanks for keeping the supported python versions up to date and checking the dependencies!