Use ::class and fix missing doc

Signed-off-by: Joas Schilling <coding@schilljs.com>

lib/private/Files/Storage/Local.php

@@ -408,10 +408,11 @@ class Local extends \OC\Files\Storage\Common {
 	 * @param IStorage $sourceStorage
 	 * @param string $sourceInternalPath
 	 * @param string $targetInternalPath
+	 * @param bool $preserveMtime
 	 * @return bool
 	 */
 	public function copyFromStorage(IStorage $sourceStorage, $sourceInternalPath, $targetInternalPath, $preserveMtime = false) {
-		if ($sourceStorage->instanceOfStorage('\OC\Files\Storage\Local')) {
+		if ($sourceStorage->instanceOfStorage(Local::class)) {
 			if ($sourceStorage->instanceOfStorage(Jail::class)) {
 				/**
 				 * @var \OC\Files\Storage\Wrapper\Jail $sourceStorage