CI: Run sdist build less often
- [ ] closes #43745
- [ ] tests added / passed
- [ ] Ensure all linting tests pass, see [here](https://pandas.pydata.org/pandas-docs/dev/development/contributing_codebase.html#pre-commit) for how to run them
- [ ] whatsnew entry

Need to test all possible combos of 
- Run on merged commits [tested]
- Run when labeled [tested]
- Skip when no "Build" label [tested]
- Run when commit pushed to labeled PR [tested]
- Run when labeled PR closed/reopened [tested]
This pull request is stale because it has been open for thirty days with no activity. Please update or respond to this comment if you're still interested in working on this. @lithomas1 is this actionable? thanks @lithomas1 