--sections-divs has no effect for Reveal.js (not documented as such)

[mcanouil]

As discovered in quarto-dev/quarto-cli#5729, --sections-divs has no effect for Reveal.js, because of how Reveal.js uses <section> tags.

Currently, this is not stated in the documentation (https://pandoc.org/MANUAL.html#option--section-divs).
Maybe worth to add a mention about --sections-divs only working for "regular" HTML documents.