Add branching_enabled to routing_options

The feature flag for advanced branching features can now be set per
group or environment wide.

This commit changes the view to use the instance variable rather than
the FeatureService directly.

Author: thomasiles

app/views/pages/conditions/_routing_options.html.erb

@@ -11,7 +11,7 @@
     <%= t("routing_page.body_routing_text") %>
   </p>
 
-  <% if FeatureService.enabled?(:branch_routing) %>
+  <% if @branching_enabled %>
   <p>
     <%= t("routing_page.body_branching_text") %>
   </p>