correct implementation of toAlarm

lib/model/requests/create_fixed_time_alarm_request.dart

@@ -12,6 +12,7 @@ class CreateFixedTimeAlarmRequest extends CreateAlarmRequest {
     : triggerAt = alarm.triggerAt,
       super(alarmType: AlarmType.timeFixed);
 
-  FixedTimeAlarm toFixedTimeAlarm(String id) =>
+  @override
+  FixedTimeAlarm toAlarm(String id) =>
       FixedTimeAlarm(id: id, triggerAt: triggerAt!);
 }