Remove a trigger from an automation

Idempotent. The automation itself is untouched; it simply stops firing on that condition. Only the automation's creator can change it; workspace owners and admins can pause or delete it. Anyone else receives 403 automation_owner_only. A system automation (include=system) is changed only by workspace owners and admins (403 workspace_agent_admin_only); any member may add a trigger to it, which runs as that member, and remove their own triggers.

_{Scope: automations:write}