security/proxytunnel: unbreak build with OpenSSL

Remove BROKEN_SSL and BROKEN_SSL_REASON from the port Makefile since the
build failure with undefined symbol SSL_get_peer_certificate can no
longer be reproduced.

The port now builds successfully in poudriere across supported FreeBSD
versions and architectures, including 13.5, 14.3, and 15.0 on both amd64
and i386.