Update v-for list example (#1628)

* Add presentation role to style-only li item

Author: chipit24

src/v2/guide/list.md

@@ -432,7 +432,7 @@ Similar to template `v-if`, you can also use a `<template>` tag with `v-for` to
 <ul>
   <template v-for="item in items">
     <li>{{ item.msg }}</li>
-    <li class="divider"></li>
+    <li class="divider" role="presentation"></li>
   </template>
 </ul>
 ```