Integrate gitlab-ci/remove-distro-images

Commit: seco-ne/yocto/infrastructure/gitlab-ci@a731b156

Remove DISTRO_IMAGES

This variable has been removed in Yocto. Its contents have been merged into DISTRO_RELEASE_ARTEFACTS.

See for reference: seco-ne/yocto/layers/meta-seconorth-distro@a316e95e