feat(nix): update allowed-users configuration

- Added "@users" and "root" to `allowed-users` in nix settings.

modules/darwin/nix/default.nix

@@ -1,7 +1,8 @@
-{ config
-, pkgs
-, lib
-, ...
+{
+  config,
+  pkgs,
+  lib,
+  ...
 }:
 with lib;
 with lib.metacfg;
@@ -32,8 +33,7 @@ in
       {
         package = cfg.package;
 
-        settings =
-          {
+        settings = {
           experimental-features = "nix-command flakes";
           http-connections = 50;
           warn-dirty = false;
@@ -50,7 +50,10 @@ in
           allow-import-from-derivation = true;
 
           trusted-users = users;
-            allowed-users = users;
+          allowed-users = [
+            "@users"
+            "root"
+          ];
 
           # NOTE: This configuration is generated by nix-installer so I'm adding it here in
           # case it becomes important.

modules/nixos/nix/default.nix

@@ -75,7 +75,10 @@ in
           sandbox = true;
           auto-optimise-store = true;
           trusted-users = users;
-          allowed-users = users;
+          allowed-users = [
+            "@users"
+            "root"
+          ];
 
           substituters = [
             cfg.default-substituter.url