Move admin-notification-setting

src/server/views/admin/legacy-slack-integration.html

@@ -7,6 +7,6 @@
 {% endblock %}
 
 {% block content_main %}
-<!-- TODO: move contents from notification settings by GW-5467  -->
+<div id="admin-notification-setting" class="admin-notification-setting"></div>
 {% endblock content_main %}