Grafana not start after upgrade and spam the slack with notification

I upgraded grafana from v6.0.2 to v9.2.4. when i turn on the alerts in grafana.ini file
[alerting]
enabled = true
grafana fail to start with this error

x grafana-server.service - Grafana instance
Loaded: loaded (/lib/systemd/system/grafana-server.service; enabled; vendor preset: enabled)
Active: failed (Result: exit-code) since Wed 2022-12-14 15:27:56 UTC; 4s ago
Docs: http://docs.grafana.org
Process: 1102 ExecStart=/usr/sbin/grafana-server --config=${CONF_FILE} --pidfile=${PID_FILE_DIR}/grafana-server.pid --packaging=deb cfg:default.paths.logs=${LOG>
Main PID: 1102 (code=exited, status=2)
CPU: 332ms

Dec 14 15:27:56 grafana-001 systemd[1]: grafana-server.service: Scheduled restart job, restart counter is at 5.
Dec 14 15:27:56 grafana-001 systemd[1]: Stopped Grafana instance.
Dec 14 15:27:56 grafana-001 systemd[1]: grafana-server.service: Start request repeated too quickly.
Dec 14 15:27:56 grafana-001 systemd[1]: grafana-server.service: Failed with result ‘exit-code’.
Dec 14 15:27:56 grafana-001 systemd[1]: Failed to start Grafana instance.

when i turn on [unified_alerting]
enabled = false
grafana spam slack with notification.