test_class.test_detach_materialized_dict_no_memory() fails randomly on the Free Threading macOS CI

macOS (free-threading) / build and test (macos-26) build: https://github.com/python/cpython/actions/runs/34757893189/job/103725487469?pr=157417

FAIL: test_detach_materialized_dict_no_memory (test.test_class.TestInlineValues.test_detach_materialized_dict_no_memory)
----------------------------------------------------------------------
test.support.isolation._RemoteTraceback: 
"""
Traceback (most recent call last):
  File "/Users/runner/work/cpython/cpython/Lib/test/support/__init__.py", line 1374, in internal
    return test(*args, **kwargs)
AssertionError: the dictionary was not cleared
"""

The above exception was the direct cause of the following exception:

Traceback (most recent call last):
  File "/Users/runner/work/cpython/cpython/Lib/test/support/__init__.py", line 1374, in internal
    return test(*args, **kwargs)
AssertionError: test failed in the subprocess

Linked PRs

• gh-157444

Start with test.test_class.TestInlineValues.test_detach_materialized_dict_no_memory and the linked macOS free-threading CI run. Reproduce the failure on the macOS-26 free-threading build, then inspect the subprocess assertion that the dictionary was not cleared. Done means the test no longer fails randomly in that CI configuration.