Update to use helpers.legacyPackages instead of helpers.packages

Builder functions have been moved to legacyPackages in fudo-nix-helpers
to satisfy nix flake check requirements.

flake.nix

@@ -19,7 +19,7 @@
       in {
         packages = rec {
           default = mebot;
-          mebot = helpers.packages."${system}".mkClojureLib {
+          mebot = helpers.legacyPackages."${system}".mkClojureLib {
             name = "org.fudo/mebot";
             src = ./.;
           };
@@ -28,7 +28,7 @@
         devShells = rec {
           default = updateDeps;
           updateDeps = pkgs.mkShell {
-            buildInputs = with helpers.packages."${system}";
+            buildInputs = with helpers.legacyPackages."${system}";
               [ (updateClojureDeps { }) ];
           };
         };