Add click_house_ci_finished_builds_sync_worker to gitlab.yml.example

What does this MR do and why?

This MR adds click_house_ci_finished_builds_sync_worker to gitlab.yml.example.

EE: true

Part of #421201 (closed)

How to set up and validate locally

Numbered steps to set up and validate the change are strongly suggested.

N/A

MR acceptance checklist

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