After revert, fixed some code base to avoid static tests failures

Author: engcom-Charlie

lib/internal/Magento/Framework/Message/Manager.php

@@ -1,7 +1,7 @@
 <?php
 /**
- * Copyright © Magento, Inc. All rights reserved.
- * See COPYING.txt for license details.
+ * Copyright 2017 Adobe
+ * All Rights Reserved.
  */
 namespace Magento\Framework\Message;
 
@@ -21,7 +21,7 @@ class Manager implements ManagerInterface
     /**
      * Default message group
      */
-    const DEFAULT_GROUP = 'default';
+    public const DEFAULT_GROUP = 'default';
 
     /**
      * @var Session

lib/internal/Magento/Framework/Message/ManagerInterface.php

@@ -1,7 +1,7 @@
 <?php
 /**
- * Copyright © Magento, Inc. All rights reserved.
- * See COPYING.txt for license details.
+ * Copyright 2017 Adobe
+ * All Rights Reserved.
  */
 namespace Magento\Framework\Message;