DOC: Improve .at indexer API docs
- [x] closes #46722 

Not sure about the wording of the `ValueError` and whether it is worth adding the additional methods under `See Also` but the same doc is used for both DataFrame and Series so I thought that mentioning all the methods is good for the sake of completeness
> under See Also but the same doc is used for both DataFrame and Series so I thought that mentioning all the methods is good for the sake of completeness

this sounds fine Hello @FactorizeD! Thanks for updating this PR. We checked the lines you've touched for [PEP 8](https://www.python.org/dev/peps/pep-0008) issues, and found:



There are currently no PEP 8 issues detected in this Pull Request. Cheers! :beers: 

##### Comment last updated at 2022-05-10 18:54:56 UTC Failing check seems not related tot his PR. Can this be merged in the current state after the check issue is resolved, or should I do something more? Thanks @FactorizeD (sorry for the delay). Failure was unrelated