pandas: DOC: fix PR02 errors in docstrings

Pandas has a script for validating docstrings:

https://github.com/pandas-dev/pandas/blob/9008ee5810c09bc907b5fdc36fc3c1dff4a50c55/ci/code_checks.sh#L72-L194

Currently, some methods fail the PR02 check.

The task here is:

• take 2-4 methods
• run: scripts/validate_docstrings.py --format=actions --errors=PR02 method-name
• check if validation docstrings passes for those methods, and if it’s necessary fix the docstrings according to whatever error is reported
• remove those methods from code_checks.sh
• commit, push, open pull request

Please don’t comment take as multiple people can work on this issue. You also don’t need to ask for permission to work on this, just comment on which methods are you going to work.

If you’re new contributor, please check the contributing guide

thanks @natmokval @mroeschke for the inspiration for this issue