GenericTable: rework timestamp formatting

controllers/ManageUsers.php

@@ -60,10 +60,8 @@ class ManageUsers extends HTMLController
 				'last_action_time' => [
 					'format' => [
 						'type' => 'timestamp',
-						'data' => [
-							'timestamp' => 'last_action_time',
-							'pattern' => 'long',
-						],
+						'pattern' => 'long',
+						'value' => 'last_action_time',
 					],
 					'header' => 'Last activity',
 					'is_sortable' => true,