message: update dummy.py documentation in the README
diff: @@ -97,8 +97,10 @@ Install the SDK: `pip install -e python/sdk`, then run the example:
  cd python/client_examples
  python dummy.py \
  --number-of-participants 1 \
  + --heartbeat-frequency 0.3 \
  --coordinator-url http://localhost:8081 \
  - --model-size 10
  + --model-size 1kB \
  + --verbose
  ```
  #### `keras_house_prices`
  