templates: Handle package.json conversion in direnv

By splitting out the check for package.yaml into a separate check, we
can avoid the constant massive shell reloads for the nix shell.

flake.nix

@@ -34,17 +34,6 @@
             yj
           ]
           ++ old.buildInputs;
-
-        shellHook =
-          ''
-            # Update package.json
-            if [ -e ./package.json ]; then
-                unlink ./package.json
-            fi
-
-            cat ./package.yaml | yj > ./package.json
-          ''
-          + old.shellHook;
       });
 
       server = nixpkgs.legacyPackages.${system}.mkShell {