appmenu: Remove "New Event" entry

The "New Event" menu item is confusing and misleading, since
it is contextless item that has a context-aware action. The
result varies depending on which view you are, but this is in
no way communicated.

So just remove that, and all the GcalWindow API that is not
used anymore altogether.

src/gcal-window.c

@@ -1604,46 +1604,6 @@ gcal_window_new_with_date (GcalApplication *app,
                        NULL);
 }
 
-/* new-event interaction: first variant */
-/**
- * gcal_window_new_event:
- * @self: a #GcalWindow
- *
- * Makes #GcalWindow create a new event.
- */
-void
-gcal_window_new_event (GcalWindow *self)
-{
-  g_autoptr (GDateTime) start_date, end_date;
-
-  /* 1st and 2nd steps */
-  set_new_event_mode (self, TRUE);
-
-  start_date = g_date_time_new_now_local ();
-
-  /* adjusting dates according to the actual view */
-  switch (self->active_view)
-    {
-    case GCAL_WINDOW_VIEW_DAY:
-    case GCAL_WINDOW_VIEW_WEEK:
-      end_date = g_date_time_add_hours (start_date, 1);
-      break;
-
-    case GCAL_WINDOW_VIEW_MONTH:
-    case GCAL_WINDOW_VIEW_YEAR:
-      end_date = g_date_time_add_days (start_date, 1);
-      break;
-
-    case GCAL_WINDOW_VIEW_LIST:
-    case GCAL_WINDOW_VIEW_SEARCH:
-    default:
-      end_date = g_date_time_add_days (start_date, 1);
-      break;
-    }
-
-  create_event_detailed_cb (NULL, start_date, end_date, self);
-}
-
 /**
  * gcal_window_set_search_mode:
  * @self: a #GcalWindow