The Dex example in docs shows the deprecated way of configuring Dex with OpenShift auth which will be removed soon from the product:
https://docs.openshift.com/container-platform/4.11/cicd/gitops/configuring-sso-on-argo-cd-using-dex.html#gitops-creating-a-new-client-in-dex_configuring-sso-for-argo-cd-using-dex

It should instead show the new way which is displayed at the bottom of the doc:
https://docs.openshift.com/container-platform/4.11/cicd/gitops/configuring-sso-on-argo-cd-using-dex.html#gitops-disable-dex-using-spec-sso_configuring-sso-for-argo-cd-using-dex