fix: agenix on nix-darwin, update flake.nix

overlays/fonts/default.nix

@@ -1,3 +1,3 @@
-{...}: (self: super: {
+_: (self: super: {
   icomoon-feather-icon-font = super.callPackage ./icomoon-feather-icon-font.nix {};
 })

overlays/fonts/icomoon-feather-icon-font.nix

@@ -30,7 +30,7 @@ stdenvNoCC.mkDerivation rec {
   meta = with lib; {
     homepage = "https://github.com/feathericons/feather";
     description = "Icomoon feather font";
-    version = version;
+    inherit version;
     longDescription = ''
       Feather is a collection of simply beautiful open source icons.
       Each icon is designed on a 24x24 grid with an emphasis on simplicity, consistency, and flexibility.