DOC: add userwarning doc about mpl #35684
- [x] closes #35684
- [x] whatsnew entry

thanks @VirosaLi 

if you'd like to backport the original change to 1.1.2 would be ok. you can do a PR vs the 1.1.2 branch directly. (if we do that we'd also need an additonal to master to move the whatsnew note). > thanks @VirosaLi
> 
> if you'd like to backport the original change to 1.1.2 would be ok. you can do a PR vs the 1.1.2 branch directly. (if we do that we'd also need an additonal to master to move the whatsnew note).

Do I need to put a note in whatsnew 1.1.2 for that?