Optimize the DAG copying of CICD sample to only copy the DAGs modified in this PR

[leahecole]

https://airflow.apache.org/docs/apache-airflow/stable/faq.html#when-there-are-a-lot-1000-of-dags-files-how-to-speed-up-parsing-of-new-files

For customers with large # of DAGs, this sample will result in all of them being marked as "modified", and as such, they'll be parsed by Airflow. Let's make sure only modified DAGs get added.