Installer updates for the August 2026 5.8.9 release

[ValClarkson]

Bumps operator image tag and all RELATED_IMAGE_* env vars to match the 5.8.9-0 images-by-tag component produced by operator-installers from release-artifacts/prerelease/developer/release-manifest-ubi9.yaml.

Calver bumped 2621 -> 2633 across all images. Content bumps from versioning.yaml:

• postgres-operator 5.8: 5.8.8-0 -> 5.8.9-0
• crunchy-postgres 15/16/17/18: 15.18/16.14/17.10/18.4 ->
  15.19/16.15/17.11/18.6
• matching -gis variants (3.3/3.4/3.5/3.6)
• crunchy-pgbackrest: 2.58.0 -> 2.59.0
• crunchy-postgres-exporter: 0.18.1 -> 0.19.1
• crunchy-pgadmin4: 9.15 -> 9.17
• crunchy-upgrade: 18.4 -> 18.6
• crunchy-pgbouncer: 1.25 (unchanged upstream, calver-only bump)

Only config/default/kustomization.yaml and config/manager/manager.yaml are touched (matches the shape of the prior 5.8.8 installer commit 426faad); make publish-public-installers is not run wholesale on REL_5_8 because its build/ tree targets the 6.0-style layout and this branch keeps the legacy simpler config/ shape.

Checklist:

• Have you added an explanation of what your changes do and why you'd like them to be included?
• Have you updated or added documentation for the change, as applicable?
• Have you tested your changes on all related environments with successful results, as applicable?
  • Have you added automated tests?

Type of Changes:

• New feature
• Bug fix
• Documentation
• Testing enhancement
• Other

What is the current behavior (link to any open issues here)?

What is the new behavior (if this is a feature change)?

• Breaking change (fix or feature that would cause existing functionality to change)

Other Information: