message: Fix flag name typo in api generator.
  The proper flag name is --packages in the create_python_api.py, and argparser is smartly resolve the names. However, it will break if a new flag with similar name is added to create_python_api.py
diff: @@ -139,7 +139,7 @@ def gen_api_init_files(
  root_init_template_flag + " --apidir=$(@D)" + output_dir +
  " --apiname=" + api_name + " --apiversion=" + str(api_version) +
  compat_api_version_flags + " " + compat_init_template_flags +
  - loading_flag + " --package=" + ",".join(packages) +
  + loading_flag + " --packages=" + ",".join(packages) +
  " --output_package=" + output_package +
  " --use_relative_imports=True $(OUTS)"
  ),
  