ERROR invalid value "json" for option --format: unknown format "json" with Juju 2.9.50

Hello,
I'm trying to deploy a simple stack and I get the following error:
```bash
$ ./generate-bundle.sh --series focal --release ussuri --ceph --ml2-ovs --name openstack-test
Creating Juju model openstack-test
Added 'openstack-test' model on prodstack/prodstack6 with credential 'stg-reproducer-marino-mrc_project' for user 'admin'

ERROR invalid value "json" for option --format: unknown format "json"
ERROR invalid value "json" for option --format: unknown format "json"
Created focal-ussuri bundle and overlays:
+ openstack/glance.yaml
+ openstack/keystone.yaml
+ openstack/neutron-gateway.yaml
+ openstack/neutron-openvswitch.yaml
+ openstack/rabbitmq-source.yaml
+ ceph/ceph.yaml
+ openstack/openstack-ceph.yaml
+ ceph/ceph-juju-storage.yaml
+ openstack/neutron-ml2dns.yaml
+ openstack/neutron-ml2dns-gateway.yaml
+ openstack/neutron-ml2dns-openvswitch.yaml
+ mysql-innodb-cluster.yaml
+ mysql-innodb-cluster-router.yaml
+ openstack/placement.yaml

Command to deploy:
juju deploy /home/ubuntu/stsstack-bundles/openstack/b/openstack-test/openstack.yaml --overlay /home/ubuntu/stsstack-bundles/openstack/b/openstack-test/o/openstack/glance.yaml --overlay /home/ubuntu/stsstack-bundles/openstack/b/openstack-test/o/openstack/keystone.yaml --overlay /home/ubuntu/stsstack-bundles/openstack/b/openstack-test/o/openstack/neutron-gateway.yaml --overlay /home/ubuntu/stsstack-bundles/openstack/b/openstack-test/o/openstack/neutron-openvswitch.yaml --overlay /home/ubuntu/stsstack-bundles/openstack/b/openstack-test/o/openstack/rabbitmq-source.yaml --overlay /home/ubuntu/stsstack-bundles/openstack/b/openstack-test/o/ceph/ceph.yaml --overlay /home/ubuntu/stsstack-bundles/openstack/b/openstack-test/o/openstack/openstack-ceph.yaml --overlay /home/ubuntu/stsstack-bundles/openstack/b/openstack-test/o/ceph/ceph-juju-storage.yaml --overlay /home/ubuntu/stsstack-bundles/openstack/b/openstack-test/o/openstack/neutron-ml2dns.yaml --overlay /home/ubuntu/stsstack-bundles/openstack/b/openstack-test/o/openstack/neutron-ml2dns-gateway.yaml --overlay /home/ubuntu/stsstack-bundles/openstack/b/openstack-test/o/openstack/neutron-ml2dns-openvswitch.yaml --overlay /home/ubuntu/stsstack-bundles/openstack/b/openstack-test/o/mysql-innodb-cluster.yaml --overlay /home/ubuntu/stsstack-bundles/openstack/b/openstack-test/o/mysql-innodb-cluster-router.yaml --overlay /home/ubuntu/stsstack-bundles/openstack/b/openstack-test/o/openstack/placement.yaml

Post-Deployment Info/Actions:

[common]
- run ./configure to initialise your deployment
- source novarc
- add rules to default security group: ./tools/sec_groups.sh`
```

I think the problem here is Juju at version 2.9.50

Regards,
Marco

Start with generate-bundle.sh and reproduce the command using Juju 2.9.50, focusing on where the --format json option is invoked. Check whether the generated bundle and overlays are valid despite the errors, and document or correct the behavior so the deployment command completes without the unknown-format message.

Written by the indexing model from the issue text.