remove outdated comment

Author: lcnr

compiler/rustc_lint/src/internal.rs

@@ -242,17 +242,10 @@ fn is_ty_or_ty_ctxt(cx: &LateContext<'_>, path: &Path<'_>) -> Option<String> {
         }
         // Only lint on `&Ty` and `&TyCtxt` if it is used outside of a trait.
         Res::SelfTyAlias { alias_to: did, is_trait_impl: false, .. } => {
-            if let ty::Adt(adt, args) = cx.tcx.type_of(did).instantiate_identity().kind() {
-                if let Some(name @ (sym::Ty | sym::TyCtxt)) = cx.tcx.get_diagnostic_name(adt.did())
-                {
-                    // NOTE: This path is currently unreachable as `Ty<'tcx>` is
-                    // defined as a type alias meaning that `impl<'tcx> Ty<'tcx>`
-                    // is not actually allowed.
-                    //
-                    // I(@lcnr) still kept this branch in so we don't miss this
-                    // if we ever change it in the future.
-                    return Some(format!("{}<{}>", name, args[0]));
-                }
+            if let ty::Adt(adt, args) = cx.tcx.type_of(did).instantiate_identity().kind()
+                && let Some(name @ (sym::Ty | sym::TyCtxt)) = cx.tcx.get_diagnostic_name(adt.did())
+            {
+                return Some(format!("{}<{}>", name, args[0]));
             }
         }
         _ => (),