Delete new postgresql chart

If we use the new postgresql chart, then auto deploy delete should delete the ${RELEASE_NAME}-postgresql chart too

Related issues:

• gitlab-org/charts/auto-deploy-app#28 (closed)
• gitlab-org/gitlab#32720 (closed)

Manual QA

• review deploy successful - https://staging.gitlab.com/hello-staging/minimal-ruby-app/-/jobs/37098751

• stop_review deploy successful - https://staging.gitlab.com/hello-staging/minimal-ruby-app/-/jobs/37098753

   Using Docker executor with image registry.gitlab.com/gitlab-org/cluster-integration/auto-deploy-image/delete-postgresql-chart:2d55ac40f8958e47ae4b46e5f1abc8288e097239 ...
  
   $ auto-deploy delete
   release "review-review-app-mfjjek" deleted
   release "review-review-app-mfjjek-postgresql" deleted
   secret "review-review-app-mfjjek-secret" deleted

• rollout 50% successful - https://staging.gitlab.com/hello-staging/minimal-ruby-app/-/jobs/37098742

• rollout 100% successul - https://staging.gitlab.com/hello-staging/minimal-ruby-app/-/jobs/37098743. delete did not delete the DB:

  $ auto-deploy delete rollout
  release "production-rollout" deleted
  secret "production-rollout-secret" deleted