[nix] Cleans up warnings about options and reduces duplication

system/hosts/altair/configuration.nix

@@ -88,11 +88,6 @@
   # Enable touchpad support (enabled default in most desktopManager).
   # services.xserver.libinput.enable = true;
 
-  # Allow unfree packages
-  nixpkgs.config = {
-    allowUnfree = true;
-  };
-
   # List packages installed in system profile. To search, run:
   # $ nix search wget
   environment.systemPackages = with pkgs; [