[AIRFLOW-2767] - Upgrade gunicorn to 19.5.0 to avoid moderate-severity CVE (#4795)
[AIRFLOW-2767] - Upgrade gunicorn to 19.5.0 to avoid moderate-severity CVE (#4795)

Upgrade gunicorn to 19.5.0 to avoid moderate-severity CVE
owlabs/incubator-airflow,owlabs/incubator-airflow,owlabs/incubator-airflow,owlabs/incubator-airflow