Remove IConnection (#2472)

src/Connections.Abstractions/IConnection.cs

@@ -1,17 +0,0 @@
-using System.Collections.Generic;
-using System.IO.Pipelines;
-using System.Threading.Tasks;
-using Microsoft.AspNetCore.Http.Features;
-
-namespace Microsoft.AspNetCore.Connections
-{
-    public interface IConnection
-    {
-        IDuplexPipe Transport { get; }
-        IFeatureCollection Features { get; }
-
-        Task StartAsync();
-        Task StartAsync(TransferFormat transferFormat);
-        Task DisposeAsync();
-    }
-}