CLN: tests/window/moments
- [x] tests added / passed
- [x] Ensure all linting tests pass, see [here](https://pandas.pydata.org/pandas-docs/dev/development/contributing_codebase.html#pre-commit) for how to run them

Reduces a lot of no-op parameterizations by creating more specific fixtures

One comment, otherwise LGTM BTW just curious, is there a gameplan for the xfails in test_online and test_expanding? > BTW just curious, is there a gameplan for the xfails in test_online and test_expanding?

Hmm those xfails are just not implemented features with associated issues I think. I don't have a timeline for tackling those yet.