Add cron trigger to cirrus.star

[IAlibay]

Towards #4216

Changes made in this Pull Request:

• Just add an extra CRON trigger to the cirrus star. I made the necessary changes on the provider.
• If it works, once end of August comes we just remove the PR trigger and we're done.

PR Checklist

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

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📚 Documentation preview 📚: https://mdanalysis--4217.org.readthedocs.build/en/4217/

[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

Patch and project coverage have no change.

Comparison is base (ac30c88) 93.62% compared to head (37ca0ce) 93.62%.

Additional details and impacted files

@@           Coverage Diff            @@
##           develop    #4217   +/-   ##
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  Coverage    93.62%   93.62%           
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  Files          193      193           
  Lines        25294    25295    +1     
  Branches      4063     4063           
========================================
+ Hits         23682    23683    +1     
  Misses        1096     1096           
  Partials       516      516           

see 1 file with indirect coverage changes

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[IAlibay]

This won't do anything until it's merged, the fact that both current Cirrus jobs are running is all the check we needed. If someone can review that'd be great, otherwise I'll review tomorrow so that I can check that Tuesday's Cron trigger is working as intended.

[IAlibay]

Self-merging to make sure we actually get to test the cron trigger this evening.