I don't think there is a need to provide 'vip unprovision' as a cli command. Network vips would be deleted with stack delete https://review.opendev.org/c/openstack/tripleo-ansible/+/798758. Also, 'vip provision' deletes all obsolete 'existing' vips for a stack.
playbook exist but not mapped to cli command
cli-overcloud- network- vip-unprovision .yaml