Docs: Bump sphinx-rtd-theme 1.2.0rc4

[benjaoming]

Checking out readthedocs/sphinx_rtd_theme#1430

Noticing that sphinxcontrib-jquery 2.0.0 loads jQuery from Google CDN... didn't recall it'd do that. 3.0.0 has it bundled in but with a bug, and I've asked for a new release.

@agjohnson we currently run Sphinx 4.5.0 with this comment in pip.in.. it'd be interesting to know if we can bump this to some 6.x version to track things a bit closer through our own documentation work.

# For intersphinx during builds
# We need these pinned to build the docs properly
Sphinx==4.5.0
docutils==0.17.1

[humitos]

We removed a lot of requirements from docs. You should update with main and re-run the pip-tools commands.

[benjaoming]

Yes, 3 hours ago :)

[benjaoming]

Well, we got it tested for a PR build, but no reason to merge, can use 1.2.0 instead :)