update workflow ref to main

[ladamski]

https://app.asana.com/1/137249556945/project/1205243787707480/task/1215113750466052?focus=true

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Note

Low Risk
CI wiring only; switches workflow ref after feature landed, with no application or security logic changes.

Overview
Updates the Privacy Review composite action so the AI classifier workflow dispatch targets main on duckduckgo/privacy-review-automation instead of the temporary branch la/triage-id-link.

Removes the in-repo comment that documented that E2E pinning. The dispatch still passes pr_url and privacy_triage_task_id unchanged. There is also a trivial whitespace trim in the Asana HTML comment body.

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