osama/cancel_old_timer_to_avoid_redundant api_calls_from_old_timers (#272)

- cancel old timer to avoid redundant api calls from old timers

Author: osama-deriv

lib/state/server_time/server_time_cubit.dart

@@ -27,6 +27,9 @@ class ServerTimeCubit extends Cubit<ServerTimeState> {
   void _connectionListener(ConnectionState state) {
     _fetchServerTime(state);
 
+    if (_serverTimeInterval != null && _serverTimeInterval!.isActive) {
+      _serverTimeInterval!.cancel();
+    }
     _serverTimeInterval = Timer.periodic(
       _fetchServerTimeDuration,
       (Timer timer) => _fetchServerTime(state),