Rustdoc: Methods from Deref should not be const

[fee1-dead]

Screenshot:

Considering that rustdoc doesn't care about const_trait_impl, methods from Deref cannot be called in const contexts. Therefore it is best to hide the const modifiers when showing methods from Deref.

[GuillaumeGomez]

For more information:

const S: String = String::new();
const Y: usize = S.len();

fn main() {}

gives:

error[E0015]: calls in constants are limited to constant functions, tuple structs and tuple variants
 --> src/main.rs:2:18
  |
2 | const Y: usize = S.len();
  |                  ^^^^^^^

error[E0493]: destructors cannot be evaluated at compile-time
 --> src/main.rs:2:18
  |
2 | const Y: usize = S.len();
  |                  ^     - value is dropped here
  |                  |
  |                  constants cannot evaluate destructors

It is linked to #67792. So for now, let's remove this display.