docs(Portal): use neutral div in landmark example (#783)

Author: johnleider

apps/docs/src/pages/components/primitives/portal.md

@@ -61,7 +61,7 @@ Teleported content lands outside your app's landmark structure — `body` is not
 ```vue
 <template>
   <Portal>
-    <aside role="region" aria-label="Chat panel">...</aside>
+    <div role="region" aria-label="Chat panel">...</div>
   </Portal>
 </template>
 ```