`test_free_threading.test_monitoring.MonitoringMisc.test_register_callback` test failure

[colesbury]

Bug report

Seen in https://github.com/python/cpython/actions/runs/12281871632/job/34272140528?pr=122564 (free threading + JIT).

Reported by @markshannon

======================================================================
FAIL: test_register_callback (test.test_free_threading.test_monitoring.MonitoringMisc.test_register_callback)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "/home/runner/work/cpython/cpython/Lib/test/test_free_threading/test_monitoring.py", line 219, in test_register_callback
    self.assertEqual(ref(), None)
    ~~~~~~~~~~~~~~~~^^^^^^^^^^^^^
AssertionError: <function MonitoringMisc.register_callback.<locals>.callback at 0x200021800f0> != None

----------------------------------------------------------------------

[colesbury]

I can't reproduce the failure in a non-JIT free threading build.

[colesbury]

The bug doesn't exist in main. It's limited to the relevant PR.