chore(files_versions): Remove unused $node variable

Signed-off-by: Louis Chemineau <louis@chmn.me>

Author: artonge

apps/files_versions/lib/Storage.php

@@ -417,8 +417,6 @@ public static function rollback(string $file, int $revision, IUser $user) {
 			$files_view->touch($file, $revision);
 			Storage::scheduleExpire($user->getUID(), $file);
 
-			$node = $userFolder->get($file);
-
 			return true;
 		} elseif ($versionCreated) {
 			self::deleteVersion($users_view, $version);