Updates egress ip firewall note in live migration docs

[stevsmit]

Version(s): 4.15, 4.16

Issue: https://issues.redhat.com/browse/OCPBUGS-42497

Link to docs preview: https://85414--ocpdocs-pr.netlify.app/openshift-enterprise/latest/networking/ovn_kubernetes_network_provider/migrate-from-openshift-sdn.html

QE review:

• [x] QE has approved this change.

Additional information:

[ocpdocs-previewbot]

🤖 Tue Nov 26 19:03:12 - Prow CI generated the docs preview:

https://85414--ocpdocs-pr.netlify.app/openshift-enterprise/latest/networking/ovn_kubernetes_network_provider/migrate-from-openshift-sdn.html

[zhaozhanqi]

/lgtm

[mburke5678]

@stevsmit A couple of comments, likely rooted in my own ignorance of the subject matter. Proceed as you see fit.

[openshift-ci[bot]]

New changes are detected. LGTM label has been removed.

[openshift-ci[bot]]

@stevsmit: all tests passed!

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[stevsmit]

/cherry-pick enterprise-4.15

[openshift-cherrypick-robot]

@stevsmit: new pull request created: #85514

In response to [this](https://github.com/openshift/openshift-docs/pull/85414#issuecomment-2501723041): >/cherry-pick enterprise-4.15 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.