First hop from 1.7.3 to 1.11.2 (docs/upgrade-k8s-1.33.md). 1.8 drops the
backup-target settings in favour of a "default" BackupTarget resource, so
the NFS target and poll interval move into defaultBackupStore. Until now
they only lived in the cluster.
Checked beforehand: no Faulted volumes, no backing images, all volumes on
engine v1.7.3, system backup pre-upgrade-v1-7-3-20261022 and Velero
backup pre-longhorn-1-8-202610221326 both complete.