Bump the required versions of Sphinx and beanbag-docutils.
Review Request #12212 — Created March 26, 2022 and submitted
This bumps Sphinx to 4.4+, which is currently the latest and is known to
compile the Review Board documentation on Python 3.
beanbag-docutils has been bumped to 1.8.1+, which is the current latest
Successfully built the documentation with these versions.