DOC: Fixing spaces around backticks, and linting
- [X] closes #21562
- [ ] tests added / passed
- [X] passes `git diff upstream/master -u -- "*.py" | flake8 --diff`
- [ ] whatsnew entry

hmm no conflicts - ok then hnm not running on travis. thanks @datapythonista 

not sure why travis doesn't didn't run on this build though......