 [DOC] Fix typo in Cheat sheet with regex
- [x ] closes #25156
- [x ] tests added / passed
   tests not needed - just a doc change
- [x ] passes `git diff upstream/master -u -- "*.py" | flake8 --diff`
  not needed - just a doc change
- [x ] whatsnew entry
   Not needed - just a doc change

Small typo fixed in Powerpoint and PDF versions of cheat sheet.

Ideally, when merged, new PDF versions should push to current pandas release.
