remove unneeded file

default.nix

@@ -1,23 +0,0 @@
-# This file defines overlays
-{inputs, ...}: {
-  # This one brings our custom packages from the 'pkgs' directory
-  additions = final: _prev: import ../pkgs final.pkgs;
-
-  # This one contains whatever you want to overlay
-  # You can change versions, add patches, set compilation flags, anything really.
-  # https://nixos.wiki/wiki/Overlays
-  modifications = final: prev: {
-    # example = prev.example.overrideAttrs (oldAttrs: rec {
-    # ...
-    # });
-  };
-
-  # When applied, the unstable nixpkgs set (declared in the flake inputs) will
-  # be accessible through 'pkgs.unstable'
-  unstable-packages = final: _prev: {
-    unstable = import inputs.nixpkgs-unstable {
-      system = final.system;
-      config.allowUnfree = true;
-    };
-  };
-}