chore: Remove system upgrade temporary files (#11255)

Refs #11241

Author: ssongliu

core/app/service/upgrade.go

@@ -218,6 +218,7 @@ func (u *UpgradeService) Upgrade(req dto.Upgrade) error {
 		_ = settingRepo.Update("SystemVersion", req.Version)
 		_ = global.AgentDB.Model(&model.Setting{}).Where("key = ?", "SystemVersion").Updates(map[string]interface{}{"value": req.Version}).Error
 		global.CONF.Base.Version = req.Version
+		_ = os.RemoveAll(downloadDir)
 		_ = settingRepo.Update("SystemStatus", "Free")
 
 		controller.RestartPanel(true, true, true)