Rollup merge of #128307 - ojeda:unescaped_backticks, r=GuillaumeGomez

Clean and enable `rustdoc::unescaped_backticks` for `core/alloc/std/test/proc_macro`

I am not sure if the lint is supposed to be "ready enough" (since it is `allow` by default), but it does catch a couple issues in `core` (`alloc`, `std`, `test` and `proc_macro` are already clean), so I propose making it `warn` in all the crates rendered in the website.

Cc: `@GuillaumeGomez`

library/core/src/ptr/mod.rs

@@ -780,7 +780,7 @@ where
 ///
 /// The caller must also ensure that the memory the pointer (non-transitively) points to is never
 /// written to (except inside an `UnsafeCell`) using this pointer or any pointer derived from it. If
-/// you need to mutate the pointee, use [`from_mut`]`. Specifically, to turn a mutable reference `m:
+/// you need to mutate the pointee, use [`from_mut`]. Specifically, to turn a mutable reference `m:
 /// &mut T` into `*const T`, prefer `from_mut(m).cast_const()` to obtain a pointer that can later be
 /// used for mutation.
 ///