Update cron workflows to not use py39

[IAlibay]

Fixes #

Changes made in this Pull Request:

PR Checklist

• Tests?
• Docs?
• CHANGELOG updated?
• Issue raised/referenced?

Developers certificate of origin

• I certify that this contribution is covered by the LGPLv2.1+ license as defined in our LICENSE and adheres to the Developer Certificate of Origin.

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📚 Documentation preview 📚: https://mdanalysis--4504.org.readthedocs.build/en/4504/

[github-actions]

Linter Bot Results:

Hi @IAlibay! Thanks for making this PR. We linted your code and found the following:

There are currently no issues detected! 🎉

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 93.63%. Comparing base (0582265) to head (6986e83).

Additional details and impacted files

@@             Coverage Diff             @@
##           develop    #4504      +/-   ##
===========================================
- Coverage    93.65%   93.63%   -0.03%     
===========================================
  Files          168      180      +12     
  Lines        21215    22294    +1079     
  Branches      3908     3908              
===========================================
+ Hits         19869    20875    +1006     
- Misses         888      961      +73     
  Partials       458      458              

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[IAlibay]

:/ looks like the job running against nightly wheels is broken - might need to fix both at the same time.