Move pytest config back to setup.cfg

[mattwthompson]

A minimal attempt at what I reference here: #2004 (comment)

Resolves #1997

• Tag issue being addressed
• Add tests
• Update docstrings/documentation, if applicable
• Lint codebase
• Update changelog

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 94.10%. Comparing base (14d16ae) to head (63d0745).
Report is 1 commits behind head on main.

Additional details and impacted files

[mattwthompson]

This seems to resolve #1997, or at least prevents the tests from not being collected.

[j-wags]

Thanks @mattwthompson - I really appreciate it, and it'll be good to have nightlies running again. I'll add a new issue to the backlog to complete the migration to pyproject.toml