message: Update INFERENCE_TO_SERVING.md
diff: @@ -24,13 +24,13 @@ 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)
  ```
  if your model file and params file are both standalone, please use the following api.
  ```
  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")
  ```
  