docs/development_setup.md instructions incorrect

[Harris Boyce]

When running export BUILD_BUILDID=$(uuidgen) && python ml_service/pipelines/diabetes_regression_build_train_pipeline.py the following error occurs:

Traceback (most recent call last):
  File "ml_service/pipelines/diabetes_regression_build_train_pipeline.py", line 6, in <module>
    from ml_service.pipelines.load_sample_data import create_sample_data_csv
ModuleNotFoundError: No module named 'ml_service'