Fix Ruff backward compatibility

shikanime · shikanime · commit a7751f682687 · 2023-01-23T10:10:44.000+01:00
diff --git a/nix/tools.nix b/nix/tools.nix
@@ -29,7 +29,7 @@
 , nodePackages
 , ormolu
 , python39Packages
-, ruff
+, ruff ? null
 , runCommand
 , rustfmt
 , shellcheck
