Remove obsolete workaround

test/Microsoft.AspNetCore.WebSockets.Test/Program.cs

@@ -1,20 +0,0 @@
-// Copyright (c) .NET Foundation. All rights reserved.
-// Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
-
-#if NET461
-using System;
-
-namespace Microsoft.AspNetCore.WebSockets.Test
-{
-    public class Program
-    {
-        public static void Main(string[] args)
-        {
-            Console.WriteLine("This Program.Main is only here to work around https://github.com/dotnet/sdk/issues/909");
-        }
-    }
-}
-#elif NETCOREAPP2_0 || NETCOREAPP2_1
-#else
-#error Target frameworks need to be updated
-#endif