Fix resize not updating events correctly

[dennis-flowscape]

[√] Flutter (Channel stable, 3.38.2, on Microsoft Windows [Version 10.0.26200.7309], locale en-SE)

Running the latest main and trying the example project's dynamic day view on Microsoft Edge does not allow resizing of events.

The callback in the resize for the DayView widget previously reported the same time for the event and the newEndTime.

onEventResized: (FlutterWeekViewEvent event, DateTime newEndTime)

This change fixes so that

• The updateEvent method no longer makes a copy before making changes
• The resize event now updates the event and passes the previous event (unchanged) and the resize drop point newEndTime