message: fix low-precision doc
diff: @@ -27,7 +27,7 @@ from paddle_serving_app.reader import RGB2BGR, Transpose, Div, Normalize
  client = Client()
  client.load_client_config(
  - "resnet_v2_50_imagenet_client/serving_client_conf.prototxt")
  + "serving_client/serving_client_conf.prototxt")
  client.connect(["127.0.0.1:9393"])
  seq = Sequential([
  @@ -37,8 +37,8 @@ seq = Sequential([
  image_file = "daisy.jpg"
  img = seq(image_file)
  -fetch_map = client.predict(feed={"image": img}, fetch=["score"])
  -print(fetch_map["score"].reshape(-1))
  +fetch_map = client.predict(feed={"image": img}, fetch=["save_infer_model/scale_0.tmp_0"])
  +print(fetch_map["save_infer_model/scale_0.tmp_0"].reshape(-1))
  ```
  ## Reference
  