Decommission pages-builder

[apburnes]

With the completion of #4456, the pages-builder components needs to be decommissioned and deleted.

Acceptance criteria

• [x] Delete the site-build-queue queue from the app, workers, and the bull board https://github.com/cloud-gov/pages-core/pull/4513
• [ ] Remove any documentation about the builder
• [ ] Delete the pages-builder- app
• [ ] Delete the builder CI pipeline
• [ ] Archive the pages-builder repo
• [x] Update any diagrams reflecting the use of the builder https://github.com/cloud-gov/cg-diagrams/pull/148