pandas: DOC: fix RT03 errors in docstrings

Pandas has a script for validating docstrings:

https://github.com/pandas-dev/pandas/blob/44c50b20e8d08613144b3353d9cd0844a53bd077/ci/code_checks.sh#L144-L414

Currently, some methods fail the RT03 check.

The task here is:

1. take 2-4 methods
2. run: scripts/validate_docstrings.py --format=actions --errors=RT03 method-name
3. check if validation docstrings passes for those methods, and if it’s necessary fix the docstrings according to whatever error is reported
4. remove those methods from code_checks.sh
5. 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.

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