[CI nightly] capm3 okd wkld ubuntu failing at workload cluster deployment

CI nightly jobs are failing continously at deploy-workload-cluster due to null value in spec.template.spec.sshAuthorizedKey

• https://gitlab.com/sylva-projects/sylva-core/-/jobs/11346041463
• https://gitlab.com/sylva-projects/sylva-core/-/jobs/11341850442
• https://gitlab.com/sylva-projects/sylva-core/-/jobs/11329572076

(Invalid): OpenshiftAssistedConfigTemplate.bootstrap.cluster.x-k8s.io "wc-2038187403-okd-capm3-virt-md0-30980b33c9" is invalid: spec.template.spec.sshAuthorizedKey: Invalid value: "null": spec.template.spec.sshAuthorizedKey in body must be of type string: "null", OpenshiftAssistedControlPlane/okd-capm3-virt/wc-2038187403-okd-capm3-virt-control-plane dry-run failed (Invalid): OpenshiftAssistedControlPlane.controlplane.cluster.x-k8s.io "wc-2038187403-okd-capm3-virt-control-plane" is invalid: [spec.config.sshAuthorizedKey: Invalid value: "null": spec.config.sshAuthorizedKey in body must be of type string: "null", spec.openshiftAssistedConfigSpec.sshAuthorizedKey: Invalid value: "null": spec.openshiftAssistedConfigSpec.sshAuthorizedKey in body must be of type string: "null"]]

cc @ionut.spanu