STY: Enable B904
I think most of the fixes should be straightforward. For a few complex cases, I think it's reasonable to `noqa` them to allow us to enable a global check to the rest of the codebase.

- [ ] closes #xxxx (Replace xxxx with the GitHub issue number)
- [ ] [Tests added and passed](https://pandas.pydata.org/pandas-docs/dev/development/contributing_codebase.html#writing-tests) if fixing a bug or adding a new feature
- [ ] All [code checks passed](https://pandas.pydata.org/pandas-docs/dev/development/contributing_codebase.html#pre-commit).
- [ ] Added [type annotations](https://pandas.pydata.org/pandas-docs/dev/development/contributing_codebase.html#type-hints) to new arguments/methods/functions.
- [ ] Added an entry in the latest `doc/source/whatsnew/vX.X.X.rst` file if fixing a bug or adding a new feature.

All tests passed after I ... added more info to debug. Not sure if I'm just unlucky with the flaky test or if there's a subtle error the test suite can't capture. 

The failed test in the previous commit is `test_dti_constructor_with_non_nano_now_today` because the diff surpasses the tolerance