net/unfs3: rescind maintainership

This port cannot be update past the current version as a dependency on
tirpc (a variant of sunrpc) was introduced in 0.10.0. Due to a conflict
with our copy of sunrpc shipped in base, I wasn't able to get tirpc to
build.

Rescind maintainership in the hope that perhaps someone else can pick
this up. Port is otherwise in working order.