gdbusconnection: Fix a false positive memory leak from scan-build

scan-build thinks that `data` could be leaked. It’s not, though; it’s
passed as the `user_data` to `g_dbus_connection_register_object()` along
with its free function.

Try and persuade scan-build that there’s no leak by annotating the
transfer.

Signed-off-by: Philip Withnall <pwithnall@gnome.org>

Helps: #1767

gio/gdbusconnection.c

@@ -5668,7 +5668,7 @@ g_dbus_connection_register_object_with_closures (GDBusConnection     *connection
                                             object_path,
                                             interface_info,
                                             &vtable,
-                                            data,
+                                            g_steal_pointer (&data),
                                             register_object_free_func,
                                             error);
 }