security/vuxml: 2.6.0 <= openvpn < 2.6.7 vulnerabilities

Related to:

PR: 275055
Security: 2fe004f5-83fd-11ee-9f5d-31909fb2f495
Security: CVE-2023-46849
Security: CVE-2023-46850

This specifically documents < 2.6.7_1 in order to collect the
regression fix for https://github.com/OpenVPN/openvpn/issues/449
which was a bug newly introduced into 2.6.7.