Auto merge of #118441 - GuillaumeGomez:display-stability-version, r=rustdoc

Always display stability version even if it's the same as the containing item

Fixes rust-lang/rust#118439.

Currently, if the containing item's version is the same as the item's version (like a method), we don't display it on the item.

This was something done on purpose as you can see [here](https://github.com/rust-lang/rust/blob/e9b7bf011478aa8c19ac49afc99853a66ba04319/src/librustdoc/html/render/mod.rs#L949-L955). It was implemented in rust-lang/rust#30686.

I think we should change this because on pages with a lot of items, if someone arrives (through the search or a link) to an item far below the page, they won't know the stability version unless they scroll to the top, which isn't great.

You can see the result [here](https://rustdoc.crud.net/imperio/display-stability-version/std/pin/struct.Pin.html#method.new).

r? `@notriddle`

Author: bors