drop unused findNixFiles function

lib/default.nix

@@ -1,17 +1,5 @@
 { lib, self, nixpkgs, ... }:
 {
-  findNixFiles = folder:
-    lib.mapAttrs'
-      (name: type:
-        if
-          type == "directory"
-        then
-          lib.nameValuePair name "${folder}/${name}"
-        else
-          lib.nameValuePair (lib.removeSuffix ".nix" name) "${folder}/${name}"
-      )
-      (builtins.readDir folder);
-
   jsonschema = import ./jsonschema { inherit lib; };
 
   buildClan = import ./build-clan { inherit lib self nixpkgs; };