Remove installing PowerShell in cibuild, this is no longer needed

[bkoelman]

All GitHub Actions runners now come preinstalled with a PowerShell version that is high enough to generate our documentation.

QUALITY CHECKLIST

• [x] Changes implemented in code
• [x] Complies with our contributing guidelines
• [ ] N/A: Adapted tests
• [ ] N/A: Documentation updated

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 90.83%. Comparing base (4e0f2a7) to head (8b0b90b). Report is 2 commits behind head on master.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #1563 +/- ## ======================================= Coverage 90.83% 90.83% ======================================= Files 348 348 Lines 11158 11158 Branches 1828 1828 ======================================= Hits 10135 10135 Misses 673 673 Partials 350 350 ```

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