Fix the broken link in contributing.md

Documentation/project-docs/contributing.md

@@ -129,7 +129,7 @@ The following file header is the used for .NET Core. Please use it for new files
 ```
 
 - See [class.cpp](../../src/vm/class.cpp) for an example of the header in a C++ file.
-- See [List.cs](https://github.com/dotnet/corefx/blob/master/src/System.Collections/src/System/Collections/Generic/List.cs) for an example of the header in a C# file.
+- See [List.cs](../../src/mscorlib/src/System/Collections/Generic/List.cs) for an example of the header in a C# file.
 
 Copying Files from Other Projects
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