Update gitlab_exporter.md to change ownership

What does this MR do and why?

The Cloud Connector team has changed direction and it does not seem to make sense for them to keep ownership of the Gitlab Exporter

Given that the overall ownership for Prometheus monitoring is currently listed as Distribution https://gitlab.com/gitlab-org/gitlab/-/tree/master/doc/administration/monitoring/prometheus one suggestion that group::distributionbuild could take ownership.

Another option that has been mentioned is that this ownership could be taken on by groupscalability Observability

Creating this MR to drive this discussion.

Thanks!

cc @cdu1