device: Do not disconnect g-authorize-method handler

Disconnecting the g-authorize-method handler is not really needed, as it
is a signal from the same object. This basically reverts 6eb9f263fd
(device: Disconnect authorization callback and remove clients) but keeps
the code to clear known clients in the dispose handler.

Closes: #91

src/device.c

@@ -200,11 +200,6 @@ static void fprint_device_dispose(GObject *object)
 	FprintDevicePrivate *priv = fprint_device_get_instance_private(self);
 
 	g_hash_table_remove_all (priv->clients);
-	g_object_disconnect (object,
-			     "g-authorize-method",
-			     G_CALLBACK (action_authorization_handler),
-			     NULL,
-			     NULL);
 
 	G_OBJECT_CLASS(fprint_device_parent_class)->dispose(object);
 }