[Maigret bot] False-positive site probe: Xing

[soxoj]

The Telegram Maigret bot auto-probe reported CLAIMED for site Xing on three random usernames.

Suggested action: Review the CONTRIBUTING.md file in this repository (playbook for fixing and adding site checks), then update this check accordingly.

[juliosuas]

Taking this one — reviewing the Xing check against CONTRIBUTING.md and will open a surgical PR (data.json / db_meta.json only).

[juliosuas]

PR up: #3175