Revert of Disable non-standard Promise functions in staging

test/mjsunit/es6/promise-internal-setter.js

Index: test/mjsunit/es6/promise-internal-setter.js
diff --git a/test/mjsunit/es6/promise-internal-setter.js b/test/mjsunit/es6/promise-internal-setter.js
index 20d361f623c2ed1aa01bbcaeec7cca779d1a58ea..83e473831666822521a28ead1a1f1b2337dfb278 100644
--- a/test/mjsunit/es6/promise-internal-setter.js
+++ b/test/mjsunit/es6/promise-internal-setter.js
@@ -1,8 +1,6 @@
 // Copyright 2015 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
-
-// Flags: --promise-extra
 
 'use strict';