Comment error in drupal_sort_css_js() - CSS_DEFAULT_GROUP instead of CSS_DEFAULT group

Minor comment error that might mislead people (misled me).

   // First order by group, so that, for example, all items in the CSS_SYSTEM
-  // group appear before items in the CSS_DEFAULT_GROUP, which appear before
+  // group appear before items in the CSS_DEFAULT group, which appear before
   // all items in the CSS_THEME group. Modules may create additional groups by
   // defining their own constants.