In https://docs.openshift.com/container-platform/4.11/updating/updating-restricted-network-cluster/restricted-network-update.html#update-restricted_updating-restricted-network-cluster, we have to get image digest from configmap that doesn't defined.
Part "Creating an image signature config map manually" where configmap is defined has been removed of documentation between 4.7 and 4.8.
https://docs.openshift.com/container-platform/4.7/updating/updating-restricted-network-cluster.html#update-configuring-image-signature
https://docs.openshift.com/container-platform/4.8/updating/updating-restricted-network-cluster/restricted-network-update.html

So since OCP 4.8 the documentation does not define how to get image digest use to update cluster.

Part "Creating an image signature config map manually" should be restore in documentation 4.8 and after.

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