Deprecate non-keyword arguments in drop
- [ ] xref #41485
- [ ] tests added / passed
- [ ] Ensure all linting tests pass, see [here](https://pandas.pydata.org/pandas-docs/dev/development/contributing.html#code-standards) for how to run them
- [ ] whatsnew entry

FYI @MarcoGorelli a way to avoid the conflicts as we merge is to put the notes slightly randomly in the whatsnew deprecation section (e.g. not one after the other) and/or put blank lines to separate the conflicts, but nbd. can u rebase Thanks @simonjayhawkins - Index.drop doesn't have inplace and the return type is always the same so I didn't prioritise it here