Panel test dialog: Clean up
Panel test dialog: Clean up

 * Remove deprecated stuff such as GtkVBox
   GtkTable and GtkHSeparator.

Signed-off-by: Alberts Muktupāvels <c88b04050faefba5a4cef1dca0ad0a969220e4f1@gmail.com>

GNOME/gnome-panel,GNOME/gnome-panel