Deprecate non-keyword arguments for drop_duplicates.
- [ ] xref #41485
- [ ] tests added / passed
- [ ] Ensure all linting tests pass
- [ ] whatsnew entry
Hello @jmholzer! 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 2021-05-24 20:25:12 UTC @MarcoGorelli I made the changes to drop_duplicates that we discussed in the comments of #41551, they are in the latest commit. @MarcoGorelli regarding the warning message generation for `MultiIndex`, I think we need to remove the `@final` decorator from `Index.drop_duplicates`, is this acceptable?

https://docs.python.org/3.8/library/typing.html#typing.final

 > @MarcoGorelli regarding the warning message generation for `MultiIndex`, I think we need to remove the `@final` decorator from `Index.drop_duplicates`, is this acceptable?
> 
> https://docs.python.org/3.8/library/typing.html#typing.final

sure. we tend to use @final to identify methods that aren't overloaded rather than methods that shouldn't be overloaded.