Fix docs for source ranges for internal NLB

[shraddhabang]

Issue

#3706

Description

The fixes the discrepancy in docs for service.beta.kubernetes.io/load-balancer-source-ranges annotation behavior for Internal NLB.

Checklist

• Added tests that cover your change (if possible)
• Added/modified documentation as required (such as the README.md, or the docs directory)
• Manually tested
• Made sure the title of the PR is a good description that can go into the release notes

BONUS POINTS checklist: complete for good vibes and maybe prizes?! 🤯

• Backfilled missing tests for code in same general area 🎉
• Refactored something and made the world a better place 🌟

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: shraddhabang, zac-nixon

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• OWNERS [shraddhabang,zac-nixon]

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[zac-nixon]

/lgtm