build-sys: next spice-protocol is 0.14.0

The requirement to the unreleased spice-protocol was added with
56c2d297 in 2019-01-28 by Lukáš Hrázký <lhrazky@redhat.com> but
next stable release of spice-protocol is 0.14.0

The configure check is correct but seems better to me to check against
a valid release instead of checking with a non existing one.

Signed-off-by: Victor Toso <victortoso@redhat.com>
Acked-by: Eduardo Lima (Etrunko) <etrunko@redhat.com>