Remove test module

modules/default.nix

@@ -1,5 +0,0 @@
-{
-  imports = [
-    ./hello.nix
-  ];
-}

modules/hello.nix

@@ -1,23 +0,0 @@
-{ lib, pkgs, config, ...}:
-
-with lib;
-let
-  cfg = config.services.hello;
-
-in {
-  options.services.hello = {
-    enable = mkEnableOption "Hello service.";
-    greeter = mkOption {
-      type = types.str;
-      default = "world";
-    };
-  };
-
-  config = mkIf cfg.enable {
-    environment.systemPackages = [
-      (pkgs.writeShellScriptBin "hello" ''
-        echo "'Hello, ${escapeShellArg cfg.greeter}!'"
-      '');
-    ];
-  };
-}