Update istio-deploy-ingress.md

[LuoPeter]

Correct a typo in internal ingress:

Use spec.clusterIPs[0]} to get INGRESS_HOST_INTERNAL.

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[Court72]

@shashankbarsin

Can you review the proposed changes?

When the changes are ready for publication, add a #sign-off comment to signal that the PR is ready for the review team to merge.

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[JoeyC-Dev]

clusterIP != internal LB IP. There is nothing wrong on current version.