Add copyright headers

Author: amcasey

src/DefaultBuilder/test/Microsoft.AspNetCore.TrimmingTests/SlimBuilderDoesNotDependOnX509Test.cs

@@ -1,3 +1,6 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+
 using Microsoft.AspNetCore.Builder;
 
 var builder = WebApplication.CreateSlimBuilder(args);

src/DefaultBuilder/test/Microsoft.AspNetCore.TrimmingTests/UseHttpsDoesDependOnX509Test.cs

@@ -1,3 +1,6 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+
 using System;
 using System.Security.Cryptography.X509Certificates;
 using Microsoft.AspNetCore.Builder;

src/DefaultBuilder/test/Microsoft.AspNetCore.TrimmingTests/X509Utilities.cs

@@ -1,3 +1,6 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+
 using System;
 using System.Diagnostics.CodeAnalysis;
 using System.Linq;