It's misleading. The main heading sometimes isn't an fully qualified name at all.
It's also redundant. It's always a child of `div.main-heading`, so just use that.
Fix reexport of `doc(hidden)` item
Part of #59368.
It doesn't fix the `doc(inline)` nor the `doc(hidden)` on macro. I'll do it in a follow-up PR.
r? `@notriddle`
