nixos: torify: disable by default, add some documentation as of why

This `tsocks` wrapper leaks DNS requests to clearnet, meanwhile Tor comes with
`torsocks` which doesn't.

Previous commits to this file state that all of this still useful somehow.
Assuming that it's true, at least let's not confuse users with two different tools
and don't clash with the `tsocks` binary from nixpkgs by disabling this by default.