Fix duplicate using directives

Author: JamesNK

src/Servers/IIS/IIS/test/Common.FunctionalTests/WebSocketInProcessTests.cs

@@ -1,7 +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.Server.IIS.FunctionalTests;
 using Microsoft.AspNetCore.InternalTesting;
 using Microsoft.AspNetCore.Server.IntegrationTesting;
 using Xunit.Abstractions;

src/Servers/IIS/IIS/test/Common.FunctionalTests/WebSocketOutOfProcessTests.cs

@@ -1,7 +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.Server.IIS.FunctionalTests;
 using Microsoft.AspNetCore.InternalTesting;
 using Microsoft.AspNetCore.Server.IntegrationTesting;
 using Xunit.Abstractions;

src/Servers/IIS/IIS/test/Common.FunctionalTests/WebSocketTests.cs

@@ -8,7 +8,6 @@
 using System.Net.WebSockets;
 using System.Text;
 using Microsoft.AspNetCore.InternalTesting;
-using Microsoft.AspNetCore.Server.IIS.FunctionalTests;
 using Microsoft.AspNetCore.Server.IntegrationTesting;
 using Microsoft.AspNetCore.Server.IntegrationTesting.IIS;
 using Xunit.Abstractions;