Gate 4.18 -> 4.20 upgrade due to admissionregistration.k8s.io/v1beta1 API removal

[jacobsee]

Add upgrade gate for the removal of admissionregistration.k8s.io/v1beta1 between 4.18 and 4.20.

[openshift-ci]

[APPROVALNOTIFIER] This PR is NOT APPROVED

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[jacobsee]

/retest-required

[jacobsee]

@sdodson Hi there, are you the right person to request a review here and also on #1193 ? If not, do you know who would be? Thanks

[jacobsee]

/retest-required

[openshift-ci]

@jacobsee: The following tests failed, say /retest to rerun all failed tests or /retest-required to rerun all mandatory failed tests:

Test name	Commit	Details	Required	Rerun command
ci/prow/okd-scos-e2e-aws-ovn	132f056	link	false	/test okd-scos-e2e-aws-ovn
ci/prow/e2e-hypershift	132f056	link	true	/test e2e-hypershift
ci/prow/e2e-hypershift-conformance	132f056	link	true	/test e2e-hypershift-conformance

Full PR test history. Your PR dashboard.

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[jacobsee]

Closing because per https://docs.redhat.com/en/documentation/openshift_container_platform/4.18/html/updating_clusters/performing-a-cluster-update#control-plane-only-update, You cannot update from OpenShift Container Platform <4.y> to <4.y+2> directly..