event: Fix changing the timezone

g_date_time_equal() corrects for timezone offsets to ensure that, e.g.,
6 AM CST is treated as equal to 12 PM UTC. This means attempts to change
the start and end times of events to the same time in another timezone
are currently failing. We need to remove this attempt at optimization
because it prevents gcal_event_set_timezone() from ever doing anything.

src/gcal-event.c

@@ -985,9 +985,7 @@ gcal_event_set_date_end (GcalEvent *self,
 {
   g_return_if_fail (GCAL_IS_EVENT (self));
 
-  if (self->dt_end != dt &&
-      (!self->dt_end || !dt ||
-       (self->dt_end && dt && !g_date_time_equal (self->dt_end, dt))))
+  if (self->dt_end != dt)
     {
       ECalComponentDateTime *component_dt, current;
 
@@ -1042,9 +1040,7 @@ gcal_event_set_date_start (GcalEvent *self,
 {
   g_return_if_fail (GCAL_IS_EVENT (self));
 
-  if (self->dt_start != dt &&
-      (!self->dt_start || !dt ||
-       (self->dt_start && dt && !g_date_time_equal (self->dt_start, dt))))
+  if (self->dt_start != dt)
     {
       ECalComponentDateTime *component_dt, current;