Remove ztunnel hairpinning from docs

[MorrisLaw]

Description

Related to #14983 (this is one of a few PRs that will be made to refresh the docs in an effort to ensure continuous progress is made as opposed to holding everything up on one big documentation PR)

Removes ztunnel hairpinning from docs since it has now been removed from the codebase. See Ztunnel PR #913.

Reviewers

• Ambient
• Docs
• Installation
• Networking
• Performance and Scalability
• Extensions and Telemetry
• Security
• Test and Release
• User Experience
• Developer Infrastructure
• Localization/Translation

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[linsun]

LGTM on removal of hairpin.

Made a comment on your clarification for out of mesh client which I think is wrong.

[MorrisLaw]

@bleggett @linsun @louiscryan I think all comments have been addressed now. PTAL again, thank you!

[linsun]

LGTM, thank you @MorrisLaw !!