fix(docs): fix up code block in the MDX guide (#7673)

fix: code block

Author: arnu515

packages/docs/src/routes/docs/(qwikcity)/guides/mdx/index.mdx

@@ -195,6 +195,7 @@ export const Tags = component$(() => {
     </ul>
   );
 });
+```
 
 ## `useContent()`
 
@@ -209,4 +210,3 @@ The `headings` array includes data about a markdown file's `<h1>` to `<h6>` [htm
 
 Menus are contextual data declared with `menu.md` files. See [menus file definition](/docs/(qwikcity)/advanced/menu/index.mdx) for more information on the file format and location.
 
-```