Remove unreferenced {} in logger.warn (AsyncHttpClient#1267)

Author: wsargent

client/src/main/java/org/asynchttpclient/netty/handler/WebSocketHandler.java

@@ -198,7 +198,7 @@ private void handleFrame(Channel channel, WebSocketFrame frame, WebSocketUpgrade
 
     @Override
     public void handleException(NettyResponseFuture<?> future, Throwable e) {
-        logger.warn("onError {}", e);
+        logger.warn("onError", e);
 
         try {
             WebSocketUpgradeHandler h = (WebSocketUpgradeHandler) future.getAsyncHandler();