Update WavChannelMask.cs

WavFile/WavChannelMask.cs

@@ -1,7 +1,5 @@
-/*
- * WavFile
- * Copyright © Wiesław Šoltés 2010-2012. All Rights Reserved
- */
+// Copyright (c) Wiesław Šoltés. All rights reserved.
+// Licensed under the MIT license. See LICENSE file in the project root for full license information.
 
 namespace WavFile
 {