Use "class" instead of "cls"

Matching docstring in feedback.js models

cms/templates/base.html

@@ -78,13 +78,13 @@
       <ul>
         <% if(actions.primary) { %>
         <li class="nav-item">
-          <a href="#" class="button action-primary <%= actions.primary.cls %>"><%= actions.primary.text %></a>
+          <a href="#" class="button action-primary <%= actions.primary.class %>"><%= actions.primary.text %></a>
         </li>
         <% } %>
         <% if(actions.secondary) {
              _.each(actions.secondary, function(secondary) { %>
         <li class="nav-item">
-          <a href="#" class="button action-secondary <%= secondary.cls %>"><%= secondary.text %></a>
+          <a href="#" class="button action-secondary <%= secondary.class %>"><%= secondary.text %></a>
         </li>
         <%   });
            } %>