Update custom-directives.md

Author: NataliaTepluhina

src/guide/migration/custom-directives.md

@@ -52,8 +52,8 @@ The final API is as follows:
 
 ```js
 const MyDirective = {
-  created() {}, // new
-  beforeMount(el, binding, vnode, prevVnode) {},
+  created(el, binding, vnode, prevVnode) {}, // new
+  beforeMount() {},
   mounted() {},
   beforeUpdate() {}, // new
   updated() {},