Remove doc(hidden) attribute that is being phased out
Remove doc(hidden) attribute that is being phased out

    warning: `#[doc(hidden)]` is ignored on trait impl items
       --> serde/src/de/impls.rs:796:5
        |
    796 |     #[doc(hidden)]
        |     ^^^^^^^^^^^^^^ help: remove this attribute
        |
        = note: `#[warn(unused_attributes)]` on by default
        = warning: this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release!
        = note: whether the impl item is `doc(hidden)` or not entirely depends on the corresponding trait item

serde-rs/serde