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Automatic merge from submit-queue. If you want to cherry-pick this change to another branch, please follow the instructions <a href="https://github.com/kubernetes/community/blob/master/contributors/devel/cherry-picks.md">here</a>. mark APIServiceSpec.CABundle optional xref: https://github.com/kubernetes/kubernetes/issues/60690#issuecomment-382842852 mark the caBundle field optional so openapi is accurate **Release note**: ```release-note NONE ```