drop python 3.9

[braingram]

Drops support for python 3.9 inline with spacetelescope/jwst#8365

Checklist

• added entry in CHANGES.rst (either in Bug Fixes or Changes to API)
• updated relevant tests
• updated relevant documentation
• updated relevant milestone(s)
• added relevant label(s)

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 64.92%. Comparing base (4d7c3a6) to head (7a7d955).
Report is 15 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #287      +/-   ##
==========================================
+ Coverage   64.84%   64.92%   +0.08%     
==========================================
  Files         103      104       +1     
  Lines        5694     5707      +13     
==========================================
+ Hits         3692     3705      +13     
  Misses       2002     2002              

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[zacharyburnett]

I was wondering why my batchpr script didn't make a PR for stdatamodels like it did for everything else, but then I realized I had typed it as spacetelescope/stadamodels in the list, so it just silently failed 😂