Update requirements/prerequisites of devfile registry helm chart

[michael-valdron]

Which area/kind this issue is related to?

/area registry

Issue Description

Prerequisites for the helm chart should be revised to better sync with the requirements for the registry operator along with a commonly shared CLUSTER_SUPPORT.md document.

Parent Epic: #1446

Acceptance Criteria

• Update supported versions of Kubernetes and OpenShift
• Add link to CLUSTER_SUPPORT.md to reference the same document

[michael-valdron]

Parent issue updated to #1446.

[github-actions]

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