[enterprise-4.15] 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/85550): >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!

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