Set default shell to bash for all ci jobs

[Wumpf]

What

Default shell varies per platform (windows uses powershell) which be quite confusing on what you can put in run and what not! This sets the default shell to bash everywhere.

Checklist

• I have read and agree to Contributor Guide and the Code of Conduct
• I've included a screenshot or gif (if applicable)
• I have tested the web demo (if applicable):
  • Using examples from latest main build: rerun.io/viewer
  • Using full set of examples from nightly build: rerun.io/viewer
• The PR title and labels are set such as to maximize their usefulness for the next release's CHANGELOG
• If applicable, add a new check to the release checklist!

• PR Build Summary
• Recent benchmark results
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