Fix CSS / Sphinx config so lists don't require line break tricks

[pushfoo]

Bug Report

Actual behavior:

ReST lists appear to omit margin spacing between their ends and subsequent elements.

To get 3.0.0 out the door quickly, I'm working around this by:

1. Adding .. raw:: html with a <br/> after
2. Commenting .. pending: post-3.0 cleanup or .. pending: #2433

Expected behavior:

ReST lists space properly