fix(cluster): update agent plan to 1.23 channel

cluster/apps/system-upgrade/system-upgrade-controller/agent-plan.yaml

@@ -9,7 +9,7 @@ metadata:
 spec:
   serviceAccountName: system-upgrade
   concurrency: 1
-  channel: https://update.k3s.io/v1-release/channels/v1.22
+  channel: https://update.k3s.io/v1-release/channels/v1.23
   nodeSelector:
     matchExpressions:
       - key: node-role.kubernetes.io/master