Update ajax.tasks.php

Too much splitting here... just realized it when I looked at Crowdin that the German translations sounds like a Google Translation - so basically ok, but obviously wrong.
Reason is that you often don't know what %s stands for and here %s was splitted up into another string with antoher %s which is definitely too much for good :/

include/ajax.tasks.php

@@ -688,8 +688,8 @@ class TasksAjaxAPI extends AjaxController {
             if (($m=$task->isCloseable()) !== true)
                 $errors['err'] = $info['error'] = $m;
             else
-                $info['warn'] = sprintf(__('Are you sure you want to %s?'),
-                        sprintf(__('change status of %s'), __('this task')));
+                $info['warn'] = sprintf(__('Are you sure you want to change status of %s?'),
+                        sprintf(__('this task'));
             break;
         default:
             Http::response(404, __('Unknown status'));