nix: fix a regression where path inputs were locked

Author: sandydoo

flake.lock

@@ -20,7 +20,7 @@
     flake = false;
   };
   inputs.nix = {
-    url = "github:cachix/nix/devenv-2.30";
+    url = "github:cachix/nix/d879e0f029613a78ec5fe3667363de5fd3c97a58";
     inputs = {
       # disabled until we fix https://github.com/cachix/devenv-nixpkgs/issues/2
       # nixpkgs.follows = "nixpkgs";