Sidebar links for methods from Deref are wrong if the type has a method of the same name

[jplatte]

On https://doc.rust-lang.org/nightly/std/vec/struct.Vec.html, there's two is_empty methods, one from Vec (why does Vec even have its own rather than relying on the slice one?? 😅) and one from [T] which Vec deref's to:

• https://doc.rust-lang.org/nightly/std/vec/struct.Vec.html#method.is_empty (Vec)
• https://doc.rust-lang.org/nightly/std/vec/struct.Vec.html#method.is_empty-1 ([T])

The link is_empty in the sidebar section "Methods from Deref<Target = [T]>" however doesn't link to the latter, it links to the former.

@rustbot labels: +T-rustdoc +A-rustdoc-ui