Fix icon.

biscuit/core/templates/core/group_full.html

@@ -13,7 +13,7 @@
       <h2>{{ group.name }} <small>{{ group.short_name }}</small></h2>
       <p>
         <a href="{% url 'edit_group_by_id' group.id %}">
-          <span class="mdi mdi-account-pencil"></span>
+          <span class="mdi mdi-pencil"></span>
         </a>
       </p>
       <h3>{% blocktrans %}Details{% endblocktrans %}</h3>