clean up corrosion systemd service

internal/machine/corrosion/systemd.go

@@ -11,22 +11,15 @@ const DefaultSystemdUnit = "uncloud-corrosion.service"
 type SystemdService struct {
 	DataDir string
 	Unit    string
-	User    string
 }
 
 func DefaultSystemdService(dataDir string) *SystemdService {
 	return &SystemdService{
 		DataDir: dataDir,
 		Unit:    DefaultSystemdUnit,
-		User:    DefaultUser,
 	}
 }
 
-func (s *SystemdService) Configure() error {
-	// TODO: create config.toml and schema dir in DataDir.
-	return nil
-}
-
 func (s *SystemdService) Start() error {
 	if _, err := exec.Command("systemctl", "start", s.Unit).Output(); err != nil {
 		return fmt.Errorf("systemctl start %s: %w", s.Unit, err)