refactor(rustc_middle): Substs -> GenericArg

compiler/rustc_trait_selection/src/traits/const_evaluatable.rs

@@ -191,7 +191,7 @@ fn satisfied_from_param_env<'tcx>(
             if let ty::ConstKind::Expr(e) = c.kind() {
                 e.visit_with(self)
             } else {
-                // FIXME(generic_const_exprs): This doesn't recurse into `<T as Trait<U>>::ASSOC`'s substs.
+                // FIXME(generic_const_exprs): This doesn't recurse into `<T as Trait<U>>::ASSOC`'s args.
                 // This is currently unobservable as `<T as Trait<{ U + 1 }>>::ASSOC` creates an anon const
                 // with its own `ConstEvaluatable` bound in the param env which we will visit separately.
                 //