message: Fix broken path in lite docs
  This fix fixes broken link in lite docs
diff: ## Recommended usage
  The Quantize Weights transformation is integrated with
  -[tflite_convert](https://github.com/tensorflow/tensorflow/blob/master/tensorflow/lite/toco/g3doc/cmdline_reference.md#transformation-flags).
  +[tflite_convert](https://github.com/tensorflow/tensorflow/blob/master/tensorflow/lite/g3doc/convert/cmdline_reference.md#transformation-flags).
  The recommended way of invoking this tool is by simply adding the
  `--post_training_quantize` flag to your original tflite_convert invocation. For
  