MDL-34650 typo correction

lib/outputcomponents.php

@@ -715,7 +715,7 @@ class single_select implements renderable {
     var $label = '';
 
     /**
-     * @var array Button label's
+     * @var array Button label's attributes
      */
     var $labelattributes = array();
 
@@ -2805,4 +2805,4 @@ class custom_menu extends custom_menu_item {
         }
         return ($itema > $itemb) ? +1 : -1;
     }
-}
\ No newline at end of file
+}