ci: send regression notifications if tests for code coverage error

[zimeg]

Summary

This PR adds the "codecov" job to lists of what regression notifications are sent for 📣

Testing

Let's hope to not find out! But earlier workflows erroring appear as:

🔗 https://github.com/slackapi/bolt-python/actions/runs/25383886159/job/74439411695

Category

• Others

Notes

• If this was intentional because of test duplication I wasn't sure, but I found the "x" on main to be confusing without having seen a notification in channel 🙏 ✨

Requirements

Please read the Contributing guidelines and Code of Conduct before creating this issue or pull request. By submitting, you are agreeing to those rules.

• I've read and understood the Contributing Guidelines and have done my best effort to follow them.
• I've read and agree to the Code of Conduct.
• I've run ./scripts/install_all_and_run_tests.sh after making the changes.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 91.32%. Comparing base (ae0ba57) to head (56a78ba).
✅ All tests successful. No failed tests found.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #1496   +/-   ##
=======================================
  Coverage   91.32%   91.32%           
=======================================
  Files         228      228           
  Lines        7262     7262           
=======================================
  Hits         6632     6632           
  Misses        630      630           

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[WilliamBergamin]

I'm not sure we should merge this 🤔

From what I understand the regression notification aren't depended on the codecov uploading, if the tests fail in the codecov that means there is some flakiness in our unittests, but I don't think we want to get notified when there is CodeCov infrastructure issue