security/openvpn: security update to 2.6.14

"Fix possible ASSERT() on OpenVPN servers using --tls-crypt-v2

Security scope: OpenVPN servers between 2.6.1 and 2.6.13 using
--tls-crypt-v2 can be made to abort with an ASSERT() message by sending
a particular combination of authenticated and malformed packets.

To trigger the bug, a valid tls-crypt-v2 client key is needed, or
network observation of a handshake with a valid tls-crypt-v2 client key

No crypto integrity is violated, no data is leaked, and no remote code
execution is possible.

This bug does not affect OpenVPN clients."

ChangeLog: https://github.com/OpenVPN/openvpn/blob/v2.6.14/Changes.rst#overview-of-changes-in-2614
Security: 2cad4541-0f5b-11f0-89f8-411aefea0df9
Security: CVE-2025-2704
MFH: 2025Q2