Update Rocky Prometheus image version

Ubuntu image build failed.

Author: markgoddard

etc/kayobe/kolla/globals.yml

@@ -14,8 +14,11 @@ kayobe_image_tags:
   openstack:
     rocky: zed-rocky-9-20230821T155947
     ubuntu: zed-ubuntu-jammy-20230821T155947
+  prometheus:
+    rocky: zed-rocky-9-20230913T160425
 
 openstack_tag: "{% raw %}{{ kayobe_image_tags['openstack'][kolla_base_distro] }}{% endraw %}"
+prometheus_tag: "{% raw %}{{ kayobe_image_tags['prometheus'][kolla_base_distro] | default(openstack_tag) }}{% endraw %}"
 
 om_enable_rabbitmq_high_availability: true