agent-monitoring prometheus instruction misleading

[bjakubski]

In https://github.com/armory/docs/blob/master/content/en/armory-enterprise/armory-agent/agent-monitoring.md
it is claimed that in order to get metrics using prometheus-operator one should created ServiceMonitor entity.
I don't see Service object being created by armory-agent helm charts, so that instruction can't be correct.
Either Service should be agged to helm chart or PodMonitor should be used instead of ServiceMonitor in documentation.