ddclient: remove unused iproute2

pkgs/tools/networking/ddclient/default.nix

···
-{ lib, fetchFromGitHub, perlPackages, autoreconfHook, iproute2, perl, curl }:
+{ lib, fetchFromGitHub, perlPackages, autoreconfHook, perl, curl }:
 
 let
   myPerl = perl.withPackages (ps: [ ps.JSONPP ]);