Make test compatible with Cache Components

Author: unstubbable

test/development/app-dir/hmr-iframe/app/layout.tsx

@@ -0,0 +1,5 @@
+import { Suspense } from 'react'
+
+export default function Root({ children }: { children: React.ReactNode }) {
+  return <Suspense>{children}</Suspense>
+}