Hide combobox navigation icons on small and extra small displays.

Signed-off-by: Roberto Rosario <roberto.rosario.gonzalez@gmail.com>

mayan/apps/appearance/templates/navigation/generic_subnavigation.html

@@ -5,7 +5,7 @@
     <li class="dropdown">
         <a href="#" class="dropdown-toggle" data-toggle="dropdown" role="button" aria-haspopup="true" aria-expanded="true">
             {% if link.icon %}
-            <i class="{{ link.icon }}"></i>
+            <i class="hidden-xs hidden-sm {{ link.icon }}"></i>
             {% endif %}
 
             {{ link.label }}