If the Prometheus service template were active, the service would be
inserted into the database during project creation. Later, the call to
`Projects::CreateService#after_create_actions` might attempt to NULL out
the service if the project didn't have any clusters that needed the
service, but this would fail with a foreign key violation since this is
enforced by the database constraint.

To fix this, we just assume if the template is present that it should
be there and skip the whole active check.

Closes https://gitlab.com/gitlab-org/gitlab/-/issues/212419