Remove allowUnfree = true from flake.nix

Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>

flake.nix

@@ -20,7 +20,6 @@
             inherit system;
             pkgs = import inputs.nixpkgs {
               inherit system;
-              config.allowUnfree = true;
             };
           }
         );