Delete REF_12_settings.py
Delete REF_12_settings.py

No longer used in course.
GoogleCloudPlatformTraining/cpd200-conference-central-python,GoogleCloudPlatformTraining/cpd200-conference-central-python,GoogleCloudPlatformTraining/cpd200-conference-central-python,GoogleCloudPlatformTraining/cpd200-conference-central-python