BUG: DataFrame.dropna must not allow to set both how= and thresh= parameters
- [x] closes #46575 
- [x] [Tests added and passed](https://pandas.pydata.org/pandas-docs/dev/development/contributing_codebase.html#writing-tests) if fixing a bug or adding a new feature
- [x] All [code checks passed](https://pandas.pydata.org/pandas-docs/dev/development/contributing_codebase.html#pre-commit).
- [x] Added an entry in the latest `doc/source/whatsnew/vX.X.X.rst` file if fixing a bug or adding a new feature.

Hello @arnaudlegout! 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 2022-04-27 16:38:33 UTC I added a what's new entry for this bug fix take @simonjayhawkins are you still waiting for something from my side, or is this PR on its way to the next release. I believe I addressed all the required changes.  @arnaudlegout this looks fine, can you merge master and ping on green. thanks @arnaudlegout 