Fix header

Author: davidwengier

src/Razor/src/Microsoft.CodeAnalysis.Razor.Workspaces/Extensions/RazorCodeDocumentExtensions_ClassifiedSpans.cs

@@ -1,5 +1,5 @@
-// Copyright (c) .NET Foundation. All rights reserved.
-// Licensed under the MIT license. See License.txt in the project root for license information.
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
 
 using System.Collections.Immutable;
 using Microsoft.AspNetCore.Razor.Language.Syntax;