#15 Fixed namespace for search base class

The namespace was changed in 3.2, so broke when backported.

classes/search/activity.php

@@ -33,6 +33,6 @@ defined('MOODLE_INTERNAL') || die();
  * @copyright  2016 Mark Nelson <markn@moodle.com>
  * @license    http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
  */
-class activity extends \core_search\base_activity {
+class activity extends \core_search\area\base_activity {
 
 }