Ingestion - Airflow default admin login and password

[mbrizbee]

Is some content missing, wrong or not clear?
On docker compose, when we try to change the default admin on airflow service, the documentation not explain that we can use "AIRFLOW_ADMIN_USER" and "AIRFLOW_ADMIN_PASSWORD".

Describe the solution you'd like
Add this on documentation

Additional context
File : https://github.com/open-metadata/OpenMetadata/blob/main/ingestion/ingestion_dependency.sh