[3.12] gh-136155: Use sphinxext-opengraph v0.12.0

[hugovk]

(cherry picked from commit c45da6a)

• Issue: Docs: EPUB builds are broken #136155

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📚 Documentation preview 📚: https://cpython-previews--136406.org.readthedocs.build/

[AA-Turner]

(misclick)

I've cherry-picked the relevant parts of #137348 and #137393 into this PR.

A

[hugovk]

The 3.13 EPUB is now good and 3.12 still has errors:

• https://docs.python.org/3.13/archives/python-3.13-docs.epub
• https://docs.python.org/3.12/archives/python-3.12-docs.epub

Let's merge and rebuild 3.12 docs.

[hugovk]

Now running:

ssh docs.nyc1.psf.io
sudo su --shell=/bin/bash docsbuild
screen -DUR  # Rejoin screen session if it exists, otherwise create a new one
/srv/docsbuild/venv/bin/python /srv/docsbuild/scripts/build_docs.py --force --branches 3.12

[hugovk]

The build completed but the 3.12 EPUB still has errors:

This is because 3.12 still has some meta tags which are not self-closing:

So we still need to backport the conditional from #137393: