Update INFERENCE_TO_SERVING_CN.md

doc/INFERENCE_TO_SERVING_CN.md

@@ -23,11 +23,11 @@ inference_model_dir = "your_inference_model"
 serving_client_dir = "serving_client_dir"
 serving_server_dir = "serving_server_dir"
 feed_var_names, fetch_var_names = inference_model_to_serving(
-		inference_model_dir, serving_client_dir, serving_server_dir)
+		inference_model_dir, serving_server_dir, serving_client_dir)
 ```
 如果模型中有模型描述文件`model_filename` 和 模型参数文件`params_filename`，那么请用
 ```
 feed_var_names, fetch_var_names = inference_model_to_serving(
-		inference_model_dir, serving_client_dir, serving_server_dir,
+		inference_model_dir, serving_server_dir, serving_client_dir,
 		 model_filename="model", params_filename="params")
 ```