Fix doc comment for ConstParamTy derive

See #111670 (comment)

Thanks @Nilstrieb for the pointer :)

Author: juntyr

library/core/src/marker.rs

@@ -986,7 +986,7 @@ pub trait PointerLike {}
 #[rustc_on_unimplemented(message = "`{Self}` can't be used as a const parameter type")]
 pub trait ConstParamTy: StructuralEq {}
 
-/// Derive macro generating an impl of the trait `Copy`.
+/// Derive macro generating an impl of the trait `ConstParamTy`.
 #[rustc_builtin_macro]
 #[unstable(feature = "adt_const_params", issue = "95174")]
 #[cfg(not(bootstrap))]