updated project linter-rules and enforced them

lib/model/timetable/timetableProps.dart

@@ -49,8 +49,8 @@ class TimetableProps extends DataHolder {
   @override
   void run({renew}) {
     GetTimetableCache(
-      startdate: int.parse(DateFormat("yyyyMMdd").format(startDate)),
-      enddate: int.parse(DateFormat("yyyyMMdd").format(endDate)),
+      startdate: int.parse(DateFormat('yyyyMMdd').format(startDate)),
+      enddate: int.parse(DateFormat('yyyyMMdd').format(endDate)),
       onUpdate: (GetTimetableResponse data) => {
         _getTimetableResponse = data,
         notifyListeners(),