Fix republishing script
Fix republishing script

All observer registries are now format-specific. There is no generic
`observers` value in the wiring any more.

ministryofjustice/specialist-publisher,alphagov/manuals-publisher,alphagov/specialist-publisher,ministryofjustice/specialist-publisher,alphagov/manuals-publisher,alphagov/specialist-publisher-rebuild,ministryofjustice/specialist-publisher,alphagov/manuals-publisher,alphagov/specialist-publisher,alphagov/specialist-publisher-rebuild,alphagov/specialist-publisher-rebuild,alphagov/specialist-publisher,alphagov/specialist-publisher-rebuild,ministryofjustice/specialist-publisher