security/fwbuilder: Deprecate abaondonware

fwbuilder fails to build for many errors due to enforced C++17
standard, i.e. throw. In addition, fwbuilder was abandoned by its
original author when he got a job with a firewall company. Since
then it's maintenance was assumed by someone on github. Unfortunately,
he made a few tweaks but failed to make any other commits since
January 2021. Therefore this port is flagged as broken under 14-CURRENT
and deperecated. It will be removed at the end of 2023Q3.

I had stopped using this port a few years ago because it didn't support
IPv6. I was hoping whoever did take on upstream maintainership on GH
would implement IPv6 support. But they didn't. Therefore I am dropping
maintainership as well.