fix(examples) remove cast in MP scripts (#2354)

After https://github.com/lvgl/lv_binding_micropython/pull/161 merged, it is no longer needed to cast the result of 'e.get_target()'

Also, additional small fixes to allow CI improvements

examples/widgets/calendar/lv_example_calendar_1.py

@@ -2,7 +2,7 @@ def event_handler(evt):
     code = evt.get_code()
 
     if code == lv.EVENT.VALUE_CHANGED:
-        source = lv.calendar.__cast__(evt.get_target())
+        source = evt.get_target()
         date = lv.calendar_date_t()
         lv.calendar.get_pressed_date(source,date)
         if date: