manually handle #1703 for note on horizontal forms

docs/templates/pages/upgrading.mustache

@@ -82,6 +82,7 @@
     <li>{{_i}}Default form style is now vertical (stacked) to use less CSS and add greater flexibility{{/i}}</li>
     <li>{{_i}}Form classes standardized with <code>.form-</code> required as a prefix{{/i}}</li>
     <li>{{_i}}New built-in form defaults for search, inline, and horizontal forms{{/i}}</li>
+    <li>{{_i}}For horizontal forms, previous classes <code>.clearfix</code> and <code>.input</code> are equivalent to the new <code>.control-group</code> and <code>.controls</code>.{{/i}}</li>
     <li>{{_i}}More flexible horizontal form markup with classes for all styling, including new optional class for the <code>label</code>{{/i}}</li>
     <li>{{_i}}Form states: colors updated and customizable via new LESS variables{{/i}}</li>
   </ul>