Remove macro_use from stable_hasher.

Normal `use` items are nicer.

compiler/rustc_data_structures/src/stable_hasher.rs

@@ -296,6 +296,8 @@ macro_rules! impl_stable_traits_for_trivial_type {
     };
 }
 
+pub(crate) use impl_stable_traits_for_trivial_type;
+
 impl_stable_traits_for_trivial_type!(i8);
 impl_stable_traits_for_trivial_type!(i16);
 impl_stable_traits_for_trivial_type!(i32);