docs: update route-groups doc to match target (sveltejs#475)

Author: jpaquim

content/tutorial/04-advanced-sveltekit/04-advanced-routing/04-route-groups/README.md

@@ -27,9 +27,9 @@ We can also add some UI to these two routes by adding a `src/routes/(authed)/+la
 
 ```svelte
 /// file: src/routes/(authed)/+layout.svelte
+<slot />
+
 <form method="POST" action="/logout">
-	<button>Log out</button>
+	<button>log out</button>
 </form>
-
-<slot />
 ```