Update bitnami/airflow Docker tag

This MR contains the following updates:

Package	Type	Update	Change
bitnami/airflow	ironbank-docker	minor	2.5.1-debian-11-r14 -> 2.6.3-debian-11-r14
bitnami/airflow		minor	2.5.1 -> 2.7.3
bitnami/airflow	stage	minor	2.5.1-debian-11-r14 -> 2.6.3-debian-11-r14

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