Fix a bunch of docs syntax
- [ ] closes #xxxx
- [ ] tests added / passed
- [ ] Ensure all linting tests pass, see [here](https://pandas.pydata.org/pandas-docs/dev/development/contributing_codebase.html#pre-commit) for how to run them
- [ ] whatsnew entry

From the Sphinx docs (https://www.sphinx-doc.org/en/master/usage/restructuredtext/directives.html#directive-versionadded):

> Note that there must be no blank line between the directive head and the explanation; this is to make these blocks visually continuous in the markup.
Actually it doesn't seem to make a difference for most of the docs so I reverted most of the changes. @jonashaag can you merge master and address comments This pull request is stale because it has been open for thirty days with no activity. Please [update](https://pandas.pydata.org/pandas-docs/stable/development/contributing.html#updating-your-pull-request) and respond to this comment if you're still interested in working on this. closing as stale (still work take if rebased)