Remove ability to use configurations without TLS by default

Remove ability to use configurations without TLS by default

OpenVPN 2.6 already warned about this feature being removed. OpenVPN
2.7 will with this change no longer accept these configurations without
having a --allow-deprecated-insecure-static-crypto added to the command
line or the configuration itself. This will serve as a last and final
warning for people who missed the warning message in OpenVPN 2.6.

This commit also removes the documentation for --secret and the static key
mode.

Change-Id: I4f29953b91cf8e8daf2c9503da44073ad96d0ff5
Signed-off-by: Arne Schwabe <arne@rfc2549.org>
Acked-by: Frank Lichtenheld <frank@lichtenheld.com>
Message-Id: <20231009105832.34762-1-frank@lichtenheld.com>
URL: https://www.mail-archive.com/openvpn-devel@lists.sourceforge.net/msg27194.html
Signed-off-by: Gert Doering <gert@greenie.muc.de>