Do not explicitly specify COS where not needed (#647)
Do not explicitly specify COS where not needed (#647)

Starting with [GKE node version 1.19](https://cloud.google.com/kubernetes-engine/docs/concepts/using-containerd#:~:text=starting%20with%20gke%20node%20version%201.19), COS image type is deprecated. I suggest to not explicitly specify any parameters where defaults would work.

Co-authored-by: Abdel SGHIOUAR <4c813a5fc22d943a524b3ed55a05e1b80e74c1aa@google.com>
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