gtknotebook: update arrow button state when reordering tabs

When reordering notebook tabs, updating the sensitivity state of the
arrow buttons is necessary if the tab is moved to the beginning or
end of the tab list.

gtk/gtknotebook.c

@@ -6774,6 +6774,7 @@ gtk_notebook_child_reordered (GtkNotebook     *notebook,
 
   gtk_widget_insert_after (page->tab_widget, notebook->tabs_widget, sibling);
 
+  update_arrow_state (notebook);
   gtk_notebook_update_labels (notebook);
   gtk_widget_queue_allocate (notebook->tabs_widget);
 }