reconcile black versions in pyproject.toml and requires-optional.txt

[gvwilson]

1. pyproject.toml specifies python>=3.8.
2. pyproject.toml also specifies black==25.1.0, which requires at least Python 3.9.
3. requires-optional.txt specifies black==22.3.0, which is compatible with Python 3.8.
4. We should pick a consistent version of black…
5. …that supports py311 and py312 (which 25.1.0 does but 22.3.0 doesn't).