security/openvpn-devel: Revert "disable ssl_testdriver test"

The cause wasn't OpenSSL 3.5 but a local tightening of the
settings, see https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=289315#c6

This reverts commit e75cace158f73d560cb09b91f4915ea9e5689115.

PR: 289315