Removed unused using

Author: mkArtakMSFT

src/Mvc/Mvc.Testing/src/WebApplicationFactory.cs

@@ -9,7 +9,6 @@
 using Microsoft.AspNetCore.Hosting;
 using Microsoft.AspNetCore.Hosting.Server;
 using Microsoft.AspNetCore.Hosting.Server.Features;
-using Microsoft.AspNetCore.Http.Features;
 using Microsoft.AspNetCore.Server.Kestrel.Core;
 using Microsoft.AspNetCore.TestHost;
 using Microsoft.Extensions.Configuration;