fix: remove PyPy from build matrix in workflows

[ianna]

see failing workflow here

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 82.63%. Comparing base (0b5ee6e) to head (7549343).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

see 2 files with indirect coverage changes

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• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.

[github-actions]

The documentation preview is ready to be viewed at http://preview.awkward-array.org.s3-website.us-east-1.amazonaws.com/PR3853

[ikrommyd]

I'm surprised this wasn't caught earlier. Do we not test wheel building on main?

[henryiii]

We test a few wheel builds, but not all of them unless manually triggered or a workflow file changes. I opened an alternative PR that simplifies the setup a bit too.