virt-viewer.spec.in: fix build after spice-xpi-client removal
This fixes commit 140cb84c2538bf0eab7dea2035dfecc4db74c784, where we
removed the spice-xpi-client-remote-viewer.
Signed-off-by: Marc-André Lureau <marcandre.lureau@redhat.com>
Reviewed-by: Daniel P. Berrange <berrange@redhat.com>