Fix accessible_class->widget_set initialization

Signed-off-by: Maks Naumov <maksqwe1@ukr.net>

https://bugzilla.gnome.org/show_bug.cgi?id=742778

gtk/a11y/gtkcontainercellaccessible.c

@@ -110,7 +110,7 @@ gtk_container_cell_accessible_class_init (GtkContainerCellAccessibleClass *klass
   class->get_n_children = gtk_container_cell_accessible_get_n_children;
   class->ref_child = gtk_container_cell_accessible_ref_child;
 
-  accessible_class->widget_unset = gtk_container_cell_widget_set;
+  accessible_class->widget_set = gtk_container_cell_widget_set;
   accessible_class->widget_unset = gtk_container_cell_widget_unset;
 
   cell_class->update_cache = gtk_container_cell_accessible_update_cache;