chore: Update flake.nix to use my preferred tools

flake.nix

@@ -7,7 +7,6 @@
     gen-luarc.url = "github:mrcjkb/nix-gen-luarc-json";
 
     # Add bleeding-edge plugins here.
-    # They can be updated with `nix flake update` (make sure to commit the generated flake.lock)
     # wf-nvim = {
     #   url = "github:Cassin01/wf.nvim";
     #   flake = false;
@@ -48,7 +47,8 @@
         buildInputs = with pkgs; [
           # Tools for Lua and Nix development, useful for editing files in this repo
           lua-language-server
-          nil
+          nixd
+          alejandra
           stylua
           luajitPackages.luacheck
         ];