remove deprecated system passing

fixes
'system' has been renamed to/replaced by 'stdenv.hostPlatform.system'

Wherever possible, it's best to reference the hostPlatform of the
nixpkgs instance directly via `config`. This is only possible in NixOS
systems though, for standalon home-manager configs we need to get that
value through `pkgs.stdenv`.

home/workmac.nix

@@ -2,14 +2,13 @@
   pkgs,
   inputs,
   config,
-  system,
   lib,
   ...
 }:
 
 with pkgs;
 let
-  unstable = inputs.nixos-unstable.legacyPackages.${system};
+  unstable = inputs.nixos-unstable.legacyPackages.${pkgs.stdenv.hostPlatform.system};
 in
 {
   imports = [ ./modules/llm.nix ];