ferm: reload rules on updates instead of restart

nixos/modules/services/networking/ferm.nix

···
       before = [ "network-pre.target" ];
       wants = [ "network-pre.target" ];
       wantedBy = [ "multi-user.target" ];
+      reloadIfChanged = true;
       serviceConfig = {
         Type="oneshot";
         RemainAfterExit = "yes";