fix(flake): Deduplicate flake-utils (#86)

* fix(flake): Deduplicate flake-utils

Both us and `poetry2nix` use `flake-utils`, let's ensure it's the same
version.

* CI: Update plugins

Author: jalil-salame

flake.lock

@@ -7,6 +7,7 @@
     poetry2nix = {
       url = "github:nix-community/poetry2nix";
       inputs.nixpkgs.follows = "nixpkgs";
+      inputs.flake-utils.follows = "flake-utils";
     };
   };