docs: close code-group in cache section (#2093)

docs/content/1.guide/5.cache.md

@@ -84,6 +84,7 @@ export default defineCachedEventHandler((event) => {
   maxAge: 60 * 60 // 1 hour
 });
 ```
+::
 
 With this example, the response will be cached for 1 hour and a stale value will be sent to the client while the cache is being updated in the background. If you want to immediately return the updated response set `swr: false`.