Breaking: Drop bundled Redis and PostgreSQL charts

What does this MR do?

Breaking: Drop bundled Redis and PostgreSQL charts

Drop the bundled Redis and PostgreSQL subcharts which were included for evaluation and PoC purposes. The deprecation was announced at https://docs.gitlab.com/update/deprecations/#support-for-bundled-postgresql-redis-and-minio-in-gitlab-helm-chart.

Relates #6281 (closed)

Changelog: removed

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• MR has a green pipeline on https://gitlab.com/gitlab-org/charts/gitlab.
• Consider downstream impact to the Operator, as per evaluating impact from changes to GitLab chart.
  • This needs gitlab-org/cloud-native/gitlab-operator!1438 (merged) to merge to not break Operator.