tests: fix license blurb in virsh-undefine

Assume commit 0466ff28 used case-insensitive replace s/OUT/EXP/
by mistake and this file is still licensed under GPLv2.0+

Undo the change.

Signed-off-by: Ján Tomko <jtomko@redhat.com>
FIxes: 0466ff28
Cc: Cole Robinson <crobinso@redhat.com>
Cc: Eric Blake <eblake@redhat.com>
Cc: Pino Toscano <ptoscano@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Reviewed-by: Cole Robinson <crobinso@redhat.com>
Reviewed-by: Pino Toscano <ptoscano@redhat.com>