nixos/brightnessctl: Remove the module

Due to the support of the systemd-logind API the udev rules aren't
required anymore which renders this module useless [0].
Note: brightnessctl should now require a working D-Bus setup and a valid
local logind session for this to work.

[0]: https://github.com/NixOS/nixpkgs/pull/79663

nixos/modules/hardware/brightnessctl.nix

@@ -1,31 +0,0 @@
-{ config, lib, pkgs, ... }:
-
-with lib;
-let
-  cfg = config.hardware.brightnessctl;
-in
-{
-
-  options = {
-
-    hardware.brightnessctl = {
-
-      enable = mkOption {
-        default = false;
-        type = types.bool;
-        description = ''
-          Enable brightnessctl in userspace.
-          This will allow brightness control from users in the video group.
-        '';
-
-      };
-    };
-  };
-
-
-  config = mkIf cfg.enable {
-    services.udev.packages = with pkgs; [ brightnessctl ];
-    environment.systemPackages = with pkgs; [ brightnessctl ];
-  };
-
-}