Import needed class

Signed-off-by: Morris Jobke <hey@morrisjobke.de>

apps/files/lib/Controller/ViewController.php

@@ -32,6 +32,7 @@ use OCA\Files\Activity\Helper;
 use OCP\AppFramework\Controller;
 use OCP\AppFramework\Http\ContentSecurityPolicy;
 use OCP\AppFramework\Http\RedirectResponse;
+use OCP\AppFramework\Http\Response;
 use OCP\AppFramework\Http\TemplateResponse;
 use OCP\App\IAppManager;
 use OCP\Files\Folder;