access denied in deploy_demo

https://stork.lab.isc.org/ has been offline for a while because of the following error in deploy_demo:

https://gitlab.isc.org/isc-projects/stork/-/jobs/2095564

Pushing agent-kea-premium (registry.gitlab.isc.org/isc-private/stork/agent-kea-premium:latest)...
The push refers to repository [registry.gitlab.isc.org/isc-private/stork/agent-kea-premium]
denied: requested access to the resource is denied
rake aborted!
Command failed with status (1): [docker-compose -f docker-compose.yaml -f d...]
/builds/isc-projects/stork/Rakefile:672:in `block in <top (required)>'
Tasks: TOP => build_and_push_demo_images