openzfs: Remove broken symlinks

These symlinks are broken. They point to files that don't exist, and
rely on having them be built using a 'in-tree' build that FreeBSD
doesn't use. They also show up as errors on grep -r. Since they are
broken and can't possibly work, remove them for now since non-functional
symlinks matching an upstrem repo that can't work in our repo aren't
worth the error messages.

Though one could argue the whole debian directory should be removed, I
did the minimal change necessary. These can return when the fundamental
issue is fixed and the contrib/debian tree is useful on FreeBSD systems.