Replace example with auth in a layout

docs/references/nextjs/auth.mdx

@@ -133,7 +133,7 @@ export async function GET() {
 
 ## Use `auth.protect()` to check if a user is authenticated
 
-`auth.protect()` can be used in a `layout.tsx` file to protect the entire route, including all children.
+`auth.protect()` can be used in a `page.tsx` file to protect any page in your application.
 
 In the following example,
 
@@ -144,10 +144,10 @@ In the following example,
 ```tsx {{ filename: 'app/dashboard/layout.tsx' }}
 import { auth } from '@clerk/nextjs/server'
 
-export default async function Layout({ children }: { children: React.ReactNode }) {
-  await auth.protect()
+export default async function Page() {
+  const { userId } = await auth.protect()
 
-  return <>{children}</>
+  return <h1>Welcome, {userId}</h1>
 }
 ```