remove windows testing on v3 branch

[jhamman]

This removes our windows test env. We can bring this back in a more modern format but this was pointing at old stuff.

TODO:

• Add unit tests and/or doctests in docstrings
• Add docstrings and API docs for any new/modified user-facing classes and functions
• New/modified features documented in docs/tutorial.rst
• Changes documented in docs/release.rst
• GitHub Actions have all passed
• Test coverage is 100% (Codecov passes)