Fix markdown of fastJoin code example (#573)

Author: matiaslopezd

docs/hooks.md

@@ -580,6 +580,7 @@ Join related records.
 - **Example using Feathers services**
 
   <p class="tip">The services in all these examples are assumed, for simplicity, to have pagination disabled. You will have to decide when to use `paginate: false` in your code.</p>
+  
   ``` js
   // project/src/services/posts/posts.hooks.js
   const { fastJoin } = require('feathers-hooks-common');
@@ -621,8 +622,6 @@ Join related records.
 
   ```
 
-  ```
-
 - **Example with recursive operations**
 
   ```js