CI/DOC: Enforce GL08 in CI
Enforce GL08 in CI so that it can be fixed and enforced in chunks like other docstring errors.

The added functions come from the result of running `scripts/validate_docstrings.py --format=actions --errors=GL08`

Part of our ongoing work to continue enforcing numpydoc validations: https://numpydoc.readthedocs.io/en/latest/validation.html#built-in-validation-checks

- [x]  xref https://github.com/pandas-dev/pandas/pull/56971
- [x] [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
- [x] 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.

pre-commit.ci autofix

 @mroeschke merge conflicts resolved in code_checks
this is the last one! 
 Thanks @jordan-d-murphy 