fixup! docs: Correct terminology in std::cmp

Replaced "this" with "this trait" in module level documentation of
`std::cmp` for `PartialEq` to be more clear.

library/core/src/cmp.rs

@@ -4,7 +4,7 @@
 //! summary:
 //!
 //! * [`PartialEq<Rhs>`] overloads the `==` and `!=` operators. In cases where
-//!   `Rhs` (the right hand side's type) is `Self`, this corresponds to a
+//!   `Rhs` (the right hand side's type) is `Self`, this trait corresponds to a
 //!   partial equivalence relation.
 //! * [`Eq`] indicates that the overloaded `==` operator corresponds to an
 //!   equivalence relation.