Confusing rustdoc layout for `const` functions that are unstable even in non-`const` contexts

[dead-claudia]

Here's what I found:

What I would've expected is something closer to this (an unstable non-const function):

For reference, functions stable in non-const contexts but unstable in const contexts look like this:

[Rua]

If the whole function is unstable, then there's no point in listing the constness as unstable, and confusing if it's given as pub fn when it's actually always const. It should just show it as pub const fn?

[camelid]

@rustbot claim