Add required fields to job cluster samples

[JaeguKim]

I found flinkoperator_v1beta1_flinkjobcluster.yaml and flinkoperator_v1beta1_remotejobjar.yaml missed required fields for v1beta1 flinkclusters.flinkoperator.k8s.io.

[google-cla[bot]]

Thanks for your pull request! It looks like this may be your first contribution to a Google open source project. Before we can look at your pull request, you'll need to sign a Contributor License Agreement (CLA).

For more information, open the CLA check for this pull request.