[enterprise-4.18] CNV-51829: added missing prereq in postinstall config section

[openshift-cherrypick-robot]

This is an automated cherry-pick of #85365

/assign kcarmichael08

[openshift-ci-robot]

@openshift-cherrypick-robot: Ignoring requests to cherry-pick non-bug issues: CNV-51829

In response to [this](https://github.com/openshift/openshift-docs/pull/85553): >This is an automated cherry-pick of #85365 > >/assign kcarmichael08 Instructions for interacting with me using PR comments are available [here](https://prow.ci.openshift.org/command-help?repo=openshift%2Fopenshift-docs). If you have questions or suggestions related to my behavior, please file an issue against the [openshift-eng/jira-lifecycle-plugin](https://github.com/openshift-eng/jira-lifecycle-plugin/issues/new) repository.

[openshift-ci[bot]]

@openshift-cherrypick-robot: all tests passed!

Full PR test history. Your PR dashboard.

Instructions for interacting with me using PR comments are available [here](https://git.k8s.io/community/contributors/guide/pull-requests.md). If you have questions or suggestions related to my behavior, please file an issue against the [kubernetes-sigs/prow](https://github.com/kubernetes-sigs/prow/issues/new?title=Prow%20issue:) repository. I understand the commands that are listed [here](https://go.k8s.io/bot-commands).