Fix unused variable 'libver' warning in Modules/_ssl.c

It can be seen on various buildbots like 3.x.cea-indiana-amd64
and 3.x.murray-snowleopard:

/export/home/buildbot/64bits/3.x.cea-indiana-amd64/build/Modules/_ssl.c:2227: warning: unused variable 'libver'

/Users/buildbot/buildarea/3.x.murray-snowleopard/build/Modules/_ssl.c:2227: warning: unused variable ‘libver’