Correct exception type.

Author: Tratcher

src/Microsoft.AspNet.Owin/WebSockets/WebSocketAdapter.cs

@@ -134,7 +134,7 @@ await _webSocket.CloseAsync(_webSocket.CloseStatus ?? WebSocketCloseStatus.Norma
                     _webSocket.Abort();
                     break;
                 default:
-                    throw new ArgumentOutOfRangeException(nameof(_webSocket.State), _webSocket.State, string.Empty);
+                    throw new NotSupportedException($"Unsupported {nameof(WebSocketState)} value: {_webSocket.State}.");
             }
         }