netclient: add network-online dependency to get rid of warning (#371276)

nixos/modules/services/networking/netclient.nix

···
   config = lib.mkIf cfg.enable {
     environment.systemPackages = [ cfg.package ];
     systemd.services.netclient = {
+      wants = [ "network-online.target" ];
       wantedBy = [ "multi-user.target" ];
       after = [ "network-online.target" ];
       description = "Netclient Daemon";