Merge pull request #111581 from helsinki-systems/revert-111451-xmonad

Revert "nixos/xmonad: add haskellPackages type"

nixos/modules/services/x11/window-managers/xmonad.nix

···
       haskellPackages = mkOption {
         default = pkgs.haskellPackages;
         defaultText = "pkgs.haskellPackages";
-        type = types.package;
         example = literalExample "pkgs.haskell.packages.ghc784";
         description = ''
           haskellPackages used to build Xmonad and other packages.