security/openvpn-devel: Update 2.7_rc3 => 2.7_rc5

Some important changes for FreeBSD users rc3 -> rc5:

• CVE 2025-15497 in epoch key handling
• repair interaction between DCO and persist-tun after reconnection
• require "script-security 2" when using --dev unix:<program>
• improve documentation and error messages for a number of deprecated options
• tun.c: unify read_tun()/write_tun() functions for all BSD platforms
• more type conversion related cleanups
• add check for auth none / cipher none on FreeBSD DCO
• drop mbedtls 2.x support

PR: 292492

Sponsored by: Subcarpathian BSD User Group

committer annotations by Matthias Andree
Approved by: Gert Doering (maintainer)

MFH: 2026Q1
(cherry picked from commit 0de0a60ce11996f82a13be4583c064f7f006b38f)