[AIRFLOW-5144] add alert on delete button click (#6745)
[AIRFLOW-5144] add alert on delete button click (#6745)

As per https://github.com/flask-admin/flask-admin/issues/1789 the deleted button did not show a confirmation alert. This issue has
been fixed in newer version of flask-admin
owlabs/incubator-airflow,owlabs/incubator-airflow,owlabs/incubator-airflow,owlabs/incubator-airflow