CNV#57055: RN 4.21 - Deprecate syntax - new virtctl port-forward / ssh / scp syntax

[danielclowers]

Version(s): 4.21

Issue: https://issues.redhat.com/browse/CNV-57055

Link to docs preview: https://104094--ocpdocs-pr.netlify.app/openshift-enterprise/latest/virt/release_notes/virt-4-21-release-notes.html#virt-4-21-deprecated_virt-4-21-release-notes

QE review:

• [ ] QE has approved this change.

Additional information:

[ocpdocs-previewbot]

🤖 Wed Dec 17 19:19:20 - Prow CI generated the docs preview:

https://104094--ocpdocs-pr.netlify.app/openshift-enterprise/latest/virt/release_notes/virt-4-21-release-notes.html

[openshift-ci[bot]]

@danielclowers: all tests passed!

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