Add HashStable_NoContext to simplify HashStable implementations in rustc_type_ir

compiler/rustc_query_system/src/ich/impls_syntax.rs

@@ -123,5 +123,3 @@ impl<'tcx> HashStable<StableHashingContext<'tcx>> for rustc_feature::Features {
         });
     }
 }
-
-impl<'ctx> rustc_type_ir::HashStableContext for StableHashingContext<'ctx> {}