Update kafka-names-cluster.yaml

Could not apply the kafka-names-cluster.yaml while practising the scenario. Found out that the yaml needs to be udpated to match new strimzi version.
The kafka-names-cluster.yaml file needs to be updated to new apiversion v1beta2 as the yaml file cannot be applied as is in the repo.
Also after updating the version, listeners defined in yaml is expected to be an array instead of object.
