Revert Merge #82310: nixos/systemd: apply .link

...even when networkd is disabled

This reverts commit ce78f3ac, reversing
changes made to dc34da07.

I'm sorry; Hydra has been unable to evaluate, always returning
> error: unexpected EOF reading a line
and I've been unable to reproduce the problem locally.  Bisecting
pointed to this merge, but I still can't see what exactly was wrong.