PostRequestAsync does not need to be generic

Author: Mpdreamz

src/Elasticsearch.Net/Connection/HttpConnection.cs

@@ -234,8 +234,8 @@ private static async Task GetResponseAsync<TReturn>(RequestData requestData, Htt
 			getResponseCancellationHandle.Unregister(((IAsyncResult) apmGetResponseTask).AsyncWaitHandle);
 		}
 
-		private static async Task PostRequestAsync<TReturn>(RequestData requestData, CancellationToken cancellationToken, HttpWebRequest request,
-			PostData<object> data) where TReturn : class
+		private static async Task PostRequestAsync(RequestData requestData, CancellationToken cancellationToken, HttpWebRequest request,
+			PostData<object> data)
 		{
 			var apmGetRequestStreamTask = Task.Factory.FromAsync(request.BeginGetRequestStream, request.EndGetRequestStream, null);
 			var getRequestStreamCancellationHandle = RegisterApmTaskTimeout(apmGetRequestStreamTask, request, requestData);