fix typo

typicode · typicode · commit c03e1fad9c57 · 2015-09-22T09:16:29.000+02:00
Missing `)`
diff --git a/source/guide/custom-filter.md b/source/guide/custom-filter.md
@@ -50,7 +50,7 @@ Vue.filter('currencyDisplay', {
       return isNaN(number) ? 0 : number
     }
   }
-}
+})
 ```
 
 Demo:
