After related charm removal the dashboards still exist

[natalytvinova]

Bug Description

Hi team,

After removing a prometheus-openstack-exporter charm that was connected to grafana via grafana-agent the dashboards from this charm are still present.

To Reproduce

juju deploy prometheus-openstack-exporter
juju deploy grafana-agent
juju relate prometheus-openstack-exporter grafana-agent
juju remove-application prometheus-openstack-exporter
Bundle:
cos--bundle.txt

Environment

Grafana-agent state:
grafana-unit.txt

Relevant log output

-

Additional context

No response

[sed-i]

Related: #303

In any case, we need an itest.