DOC: a few sphinx fixes in release notes
- [ ] closes #xxxx
- [ ] tests added / passed
- [ ] passes `black pandas`
- [ ] passes `git diff upstream/master -u -- "*.py" | flake8 --diff`
- [ ] whatsnew entry

I've labelled 1.1.3 but only the changes in doc/source/whatsnew/v1.1.3.rst can be backported.