remove unused use statement

src/Controller/MediaSourceController.php

@@ -5,7 +5,6 @@ namespace Drupal\islandora\Controller;
 use Drupal\Core\Access\AccessResult;
 use Drupal\Core\Controller\ControllerBase;
 use Drupal\Core\Database\Connection;
-use Drupal\Core\File\FileSystemInterface;
 use Drupal\Core\Routing\RouteMatch;
 use Drupal\Core\Session\AccountInterface;
 use Drupal\media\Entity\Media;