Draft: Update bitnami/airflow Docker tag to v2.8.1

This MR contains the following updates:

Package	Type	Update	Change
bitnami/airflow		minor	2.7.3 -> 2.8.1
bitnami/airflow	ironbank-docker	minor	2.7.3-debian-11-r6 -> 2.8.1-debian-11-r6
bitnami/airflow	stage	minor	2.7.3-debian-11-r6 -> 2.8.1-debian-11-r6

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