CLN: assorted cleanups
@datapythonista is there an easy way to run the docstring validation on non-public/non-API functions?  here im thinking of tslibs.ccalendar

(side-note, does the docstring validation check that type annotations match docstring parameters and return types?) The script runs on all public functions/methods when called without parameters, but it can run on private functions if you pass it as parameter (e.g. `./scripts/validate_docstrings.py pandas.Series._private_method`).

We don't check type annotations at the moment, but I guess shouldn't be difficult to implement it. The script now lives in numpydoc, I'm already working on replacing our version by the one in numpydoc. @WillAyd @mroeschke this is pretty spread out.  LMK if there are pieces I can split out that you'd be comfortable merging. looks fine, happy to merge now and follow up with those 2 issues or repush, lmk. thanks @jbrockmendel 