BUG: DataFrame.at with non-unique axes
- [x] closes #33041
- [x] tests added / passed
- [x] passes `black pandas`
- [x] passes `git diff upstream/master -u -- "*.py" | flake8 --diff`
- [x] whatsnew entry

Closes #33041 in conjunction with #33045.
i think consensus on the call was to move forward with this? gentle ping > i think consensus on the call was to move forward with this?

Yes, as also summarized on the issue (#33153)
 gentle ping Thanks! 

(BTW, if you have 2 approvals and no others commenting/requesting changes, I think it is fine to merge yourself) > BTW, if you have 2 approvals and no others commenting/requesting changes, I think it is fine to merge yourself

Good rule of thumb, thanks