project: Make time format a first-class citizen

The current code deals with 12/24h clock formats almost like
a workaround of the issue. This commit adds proper support to
different clock formats.

src/views/gcal-week-header.c

@@ -86,8 +86,6 @@ struct _GcalWeekHeader
    */
   gboolean            expanded;
 
-  gboolean            use_24h_format;
-
   icaltimetype       *active_date;
 
   gint                selection_start;
@@ -1834,15 +1832,6 @@ gcal_week_header_set_first_weekday (GcalWeekHeader *self,
   self->first_weekday = nr_day;
 }
 
-void
-gcal_week_header_set_use_24h_format (GcalWeekHeader *self,
-                                     gboolean        use_24h_format)
-{
-  g_return_if_fail (GCAL_IS_WEEK_HEADER (self));
-
-  self->use_24h_format = use_24h_format;
-}
-
 void
 gcal_week_header_add_event (GcalWeekHeader *self,
                             GcalEvent      *event)