Update source quality ratings for pg_pipeline

Why is this change being made?

This change completes https://gitlab.com/gitlab-data/analytics/issues/3455 which now gives us full visibility into what data sources need additional work to get them to quality rating 2 before we start adding metrics and alerts via Thanos.

Does this MR meet the acceptance criteria?

Conformity

• Added description to this MR explaining the reasons for the proposed change, per say-why-not-just-what