views: use the new GcalClock to redraw

Instead of having each view manage it's own timeout (or
even worse, making GcalWindow manage it), use the newly
introduced GcalClock API to do that.

src/views/gcal-month-view.c

@@ -2307,4 +2307,9 @@ gcal_month_view_set_manager (GcalMonthView *self,
   g_return_if_fail (GCAL_IS_MONTH_VIEW (self));
 
   self->manager = manager;
+
+  g_signal_connect_swapped (gcal_manager_get_clock (manager),
+                            "day-changed",
+                            G_CALLBACK (gtk_widget_queue_draw),
+                            self);
 }