Use :guilabel: markup in IDLE doc

[StanFromIreland]

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📚 Documentation preview 📚: https://cpython-previews--141371.org.readthedocs.build/

[StanFromIreland]

@terryjreedy could you take a look please?

[terryjreedy]

I don't understand what is going on with & and underlines. The github .rst diff above shows the E of Edit underlined, as does the resulting preview. But the unchanged suggestion (with 'suggestion tag removed')

Output windows, such as used for :menuselection:`&Edit --> Find in Files`,

does not. This suggests that there is no underline in the revised text (and how could there be) and that gh is slightly lying as to the file content. I found the guilabel and menuselection doc in the devguide but no mention of & as inline text markup in the devguide or reST docs. Can you explain?

I still need to check the IDLE's Help --> IDLE doc result produced by help.py.

[It occurs to me that IDLE could improve upon Sphinx's html, and not just copy it, by adding color, but this would be follow-up issue, enabled by this one.]

[StanFromIreland]

Can you explain?

The Sphinx docs can :-)

IDLE's Help --> IDLE doc result produced by help.py.

I added one to the PR description.