Remove superfluous x509_write_pem()

Remove superfluous x509_write_pem()

After removing --tls-export-cert, this function was left in the code
base with no other users.  This was an oversight in the previous
change.  Removing it to avoid leaving dead code behind.

Signed-off-by: David Sommerseth <davids@openvpn.net>
Acked-by: Gert Doering <gert@greenie.muc.de>
Message-Id: <20231122190057.120384-1-dazo+openvpn@eurephia.org>
URL: https://www.mail-archive.com/openvpn-devel@lists.sourceforge.net/msg27561.html
Signed-off-by: Gert Doering <gert@greenie.muc.de>