[gnome-control-center] printers: Add note about callback that passed ownership

[Robert Ancell <rancell src gnome org>]

commit 81392210f2ea100e1bdd0111d929769082fc8391
Author: Robert Ancell <robert ancell canonical com>
Date:   Fri Feb 12 15:22:17 2021 +1300

    printers: Add note about callback that passed ownership

 panels/printers/pp-utils.h | 1 +
 1 file changed, 1 insertion(+)
---
diff --git a/panels/printers/pp-utils.h b/panels/printers/pp-utils.h
index 34762ff33..f1d840ffc 100644
--- a/panels/printers/pp-utils.h
+++ b/panels/printers/pp-utils.h
@@ -218,6 +218,7 @@ void        printer_get_ppd_async (const gchar *printer_name,
                                    PGPCallback  callback,
                                    gpointer     user_data);
 
+/* NOTE: 'destination' is passed with ownership as cupsCopyDest doesn't seem to work as expected */
 typedef void (*GNDCallback) (cups_dest_t *destination,
                              gpointer     user_data);