Correct `SynchronousReadAndWriteTests.ReadAndWriteSynchronously` test

[dougbu]

Failed in https://dev.azure.com/dnceng/public/_build/results?buildId=828460&view=ms.vss-test-web.build-test-results-tab&runId=26407056&resultId=123619&paneView=debug with the following information in the pipeline:

System.Net.Http.HttpRequestException : Error while copying content to a stream.
---- System.IO.IOException : Unable to read data from the transport connection: An existing connection was forcibly closed by the remote host..
-------- System.Net.Sockets.SocketException : An existing connection was forcibly closed by the remote host.

Stack trace
   at System.Net.Http.HttpContent.LoadIntoBufferAsyncCore(Task serializeToStreamTask, MemoryStream tempBuffer)
   at Microsoft.AspNetCore.Server.IntegrationTesting.IIS.LoggingHandler.LogResponse(LogLevel logLevel, HttpResponseMessage response) in /_/src/Servers/IIS/IntegrationTesting.IIS/src/LoggingHandler.cs:line 39
   at Microsoft.AspNetCore.Server.IntegrationTesting.IIS.LoggingHandler.SendAsync(HttpRequestMessage request, CancellationToken cancellationToken) in /_/src/Servers/IIS/IntegrationTesting.IIS/src/LoggingHandler.cs:line 32
   at System.Net.Http.HttpClient.SendAsyncCore(HttpRequestMessage request, HttpCompletionOption completionOption, Boolean async, Boolean emitTelemetryStartStop, CancellationToken cancellationToken)
   at Microsoft.AspNetCore.Server.IIS.FunctionalTests.InProcess.SynchronousReadAndWriteTests.ReadAndWriteSynchronously() in /_/src/Servers/IIS/IIS/test/Common.FunctionalTests/Inprocess/SynchronousReadAndWriteTests.cs:line 30
--- End of stack trace from previous location ---
----- Inner Stack Trace -----
   at System.Net.Sockets.Socket.AwaitableSocketAsyncEventArgs.ThrowException(SocketError error, CancellationToken cancellationToken)
   at System.Net.Sockets.Socket.AwaitableSocketAsyncEventArgs.GetResult(Int16 token)
   at System.Net.Http.HttpConnection.FillAsync(Boolean async)
   at System.Net.Http.HttpConnection.ChunkedEncodingReadStream.CopyToAsyncCore(Stream destination, CancellationToken cancellationToken)
   at System.Net.Http.HttpConnectionResponseContent.SerializeToStreamAsync(Stream stream, TransportContext context, CancellationToken cancellationToken)
   at System.Net.Http.HttpContent.LoadIntoBufferAsyncCore(Task serializeToStreamTask, MemoryStream tempBuffer)
----- Inner Stack Trace -----

Information matches what's shown in https://helixre107v0xdeko0k025g8.blob.core.windows.net/dotnet-aspnetcore-refs-heads-release-50-rc2-02ebf0303e104c1cbc/IIS.NewHandler.FunctionalTests--net5.0/console.beaf8808.log?sv=2019-07-07&se=2020-10-14T02%3A12%3A24Z&sr=c&sp=rl&sig=KsAwezKriujISZDzwmIsSligoL5%2Blle6VB%2Bz2v%2FFs%2B0%3D but the https://helixre107v0xdeko0k025g8.blob.core.windows.net/dotnet-aspnetcore-refs-heads-release-50-rc2-02ebf0303e104c1cbc/IIS.NewHandler.FunctionalTests--net5.0/SynchronousReadAndWriteTests_ReadAndWriteSynchronously.log file looks surprisingly good.

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We're moving this issue to the Next sprint planning milestone for future evaluation / consideration. We will evaluate the request when we are planning the work for the next milestone. To learn more about what to expect next and how this issue will be handled you can read more about our triage process here.

[HaoK]

This is passing at a high rate (100% last 30 days), could be a candidate for retry parole