C# merge fixups

src/csharp/Grpc.Core.Tests/Internal/AsyncCallTest.cs

@@ -210,6 +210,7 @@ namespace Grpc.Core.Internal.Tests
                 new Metadata());
 
             AssertUnaryResponseSuccess(asyncCall, fakeCall, resultTask);
+
             var writeTask = requestStream.WriteAsync("request1");
             var ex = Assert.ThrowsAsync<RpcException>(async () => await writeTask);
             Assert.AreEqual(Status.DefaultSuccess, ex.Status);

src/csharp/Grpc.Core/Channel.cs

@@ -31,7 +31,6 @@
 
 using System;
 using System.Collections.Generic;
-using System.Linq;
 using System.Threading;
 using System.Threading.Tasks;