(split out from #30315)

We propose to downgrade jmol to optional.

It used to be needed for

• HTML docbuild (not any more, as of Sage 10.5.beta2) -> sagemath_doc_html: Use jupyter-sphinx for 3D graphics #33507
• sagetex testsuite (not any more, as of Sage 10.5.beta2)
• PDF docbuild (not any more, as of Sage 10.5.beta2)

See discussion: ​https://groups.google.com/g/sage-devel/c/qKqTmLzHAbg/m/6YxQ_qWUBQAJ
and #33507 for alternative technologies for creating 3D graphics for documentation and sagetex

Depends on #33507
Depends on #33534

CC: @kcrisman @novoselt @jcamp0x2a @antonio-rojas @kiwifb @seblabbe @egourgoulhon @dimpase

Component: build

Author: Matthias Koeppe

Issue created by migration from https://trac.sagemath.org/ticket/31027