Update what's new page with relevant issues for df.query() with in-pl…
- [x] closes #10486
- [N/A] tests added / passed
- [x] passes `git diff upstream/master | flake8 --diff`
- [x] whatsnew entry

…ace operator

The relevant issues added are :
BUG: query with invalid dtypes should fallback to python engine #10486
BUG: query modifies the frame when you compare with `=` #8664

this is actually editing an old whatsnew but ok.
