[enterprise-4.16] OSDOCS-8938: Cluster notifications docs for Managed OpenShift

[openshift-cherrypick-robot]

This is an automated cherry-pick of #75710

/assign adellape

[openshift-ci-robot]

@openshift-cherrypick-robot: Ignoring requests to cherry-pick non-bug issues: OSDOCS-8938

In response to this:

This is an automated cherry-pick of #75710

/assign adellape

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[ocpdocs-previewbot]

🤖 Tue May 28 21:02:11 - Prow CI generated the docs preview:
https://76611--ocpdocs-pr.netlify.app
Complete list of updated preview URLs: artifacts/updated_preview_urls.txt

[openshift-ci]

@openshift-cherrypick-robot: all tests passed!

Full PR test history. Your PR dashboard.

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