[KEYCLOAK-9460] Fixes obsolete Prometheus API call
[KEYCLOAK-9460] Fixes obsolete Prometheus API call

* Prometheus client: update usage (previously used obsolete prometheus.Handle())

Signed-off-by: Frederic BIDON <58692fd42329d32571d999fbcdd2ddd08a5186db@oneconcern.com>

gambol99/keycloak-proxy