add postgres version to subsequent helm deploys

If the postgres image version isn't passed to upgrades, helm will revert to the default postgres version. If it crosses incompatible version boundaries, this will break postgres horribly, as it won't be able to read the data files.

changelogs/unreleased/fix-autodevops-postgres-versioning.yml

+---
+title: Fixed ignored postgres version that occurs after the first autodevops deploy when specifying custom $POSTGRES_VERSION
+merge_request: 28735
+author: Brandon Dimcheff
+type: fixed

lib/gitlab/ci/templates/Jobs/Deploy.gitlab-ci.yml

@@ -432,6 +432,7 @@ rollout 100%:
         --set postgresql.postgresUser="$POSTGRES_USER" \
         --set postgresql.postgresPassword="$POSTGRES_PASSWORD" \
         --set postgresql.postgresDatabase="$POSTGRES_DB" \
+        --set postgresql.imageTag="$POSTGRES_VERSION" \
         --set application.migrateCommand="$DB_MIGRATE" \
         $HELM_UPGRADE_EXTRA_ARGS \
         --namespace="$KUBE_NAMESPACE" \