python312Packages.async-generator: disable failing test

There is little hope for this package, but jupyterhub still depends on
it, while upstream wants to deprecate it.

pkgs/development/python-modules/async-generator/default.nix

@@ -1,6 +1,7 @@
 { lib
 , buildPythonPackage
 , fetchPypi
+, pythonAtLeast
 , pythonOlder
 , pytestCheckHook
 }:
@@ -22,6 +23,10 @@ buildPythonPackage rec {
     pytestCheckHook
   ];
 
+  disabledTests = lib.optionals (pythonAtLeast "3.12") [
+    "test_aclose_on_unstarted_generator"
+  ];
+
   pythonImportsCheck = [ "async_generator" ];
 
   meta = with lib; {