Fix display of enums with subfields

[jsha]

https://docs.rs/xmlparser/0.13.4/xmlparser/enum.Token.html

(I've expanded one of the "Show fields" toggles in the above screenshot)

Problems:

• The font weight of "Fields of Comment" is higher than the font weight of the "Comment" heading above it. "Comment" should be larger and heavier weight - similar to the weight of methods. And "Fields of _" should be lightweight.
• "Fields of Comment" is an <h3>, but "Comment" is not a heading at all. This should be reversed.

EDIT(camelid): The toggles seen in the image above have already been removed. See #90061 (comment) for an updated screenshot.

[camelid]

I'm pretty sure I got rid of the variant fields toggle a couple months ago; those docs were generated back in June. So I think the toggle-related problems have already been fixed :)

EDIT: I removed the toggles in #87332.

[jsha]

Confirmed. Here's what it looks like built with nightly:

Thanks for fixing the toggles!

[camelid]

The font weight of "Fields of Comment" is higher than the font weight of the "Comment" heading above it. "Comment" should be larger and heavier weight - similar to the weight of methods. And "Fields of _" should be lightweight.

I fully agree with this. I find the current styling very confusing to look at. Also, I think we should replace "Fields of Comment" with just "Fields" — it's more consistent with other parts of the docs and less redundant.