[DOCS] Add `ssl.verification_mode` to secure settings

[lockewritesdocs]

Adds documentation for the xpack.security.http.ssl.verification_mode setting in the secure settings page, and removes this setting from the docker-compose.yml file in the Docker installation guide.

Closes #85375

[github-actions[bot]]

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[elasticsearchmachine]

Pinging @elastic/es-docs (Team:Docs)

[elasticsearchmachine]

Pinging @elastic/es-security (Team:Security)

[lockewritesdocs]

@ywangd, I updated the existing definition for verification_mode so that it can be used consistently throughout the TLS/SSL pages. This is a much cleaner implementation, so thanks for pointing out the existing block so that we can improve reuse and have cleaner source code ✋ 5️⃣ Please re-review when you can.

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[abdonpijpelink]

Closing unmerged in favor of #93083.