Unlink Subtask

curl --request DELETE \
  --url https://api.example.com/agents/tasks/{task_id}/subtasks/{child_id}

{
  "detail": [
    {
      "loc": [
        "<string>"
      ],
      "msg": "<string>",
      "type": "<string>",
      "input": "<unknown>",
      "ctx": {}
    }
  ]
}