distro/pkg/nix: drop restriction on jinja2 version

distro/pkg/nix/default.nix

@@ -14,6 +14,11 @@ python3Packages.buildPythonApplication rec {
     sha256 = "FIXME"; # would be {{ src_hash }} if tarball was used
   };
 
+  # Old jinja2 isn't in nixpkgs anymore.
+  postPatch = ''
+    substituteInPlace setup.cfg --replace 'jinja2<3.1' 'jinja2'
+  '';
+
   propagatedBuildInputs = with python3Packages; [
     # copy&pasted requirements.txt (almost exactly)
     beautifulsoup4   # upstream version detection