fix notify pydantic model_attributes_type

[QSummerY]

422 {"detail":[{"type":"model_attributes_type","loc":["body"],"msg":"Input should be a valid dictionary or object to extract fields from","input":"{\"phase\":\"request\",\"title\":\"在指定机器上执行ncdu命令\",\"ticket_url\":\"http://localhost:8123/ticket/10\",\"status\":\"pending\",\"is_approved\":false,\"submitter\":\"\",\"params\":{\"reason\":\"test\",\"instance\":\"\",\"alertname\":\"\",\"mountpoint\":\"/\"},\"request_time\":\"2026-05-09T20:11:19+08:00\",\"reason\":\"test\",\"approval_flow\":\"default\",\"current_node\":\"cc\",\"approvers\":\"\",\"next_node\":\"\",\"approval_log\":[],\"notify_type\":\"approval\",\"notify_people\":\"\",\"comfirmed_by\":\"\"}"}]}