pythongh-118413: Temporarily skip test_release_task_refs in free-th…

…readed builds (python#118491)

Lib/test/_test_multiprocessing.py

@@ -2804,6 +2804,7 @@ def test_map_no_failfast(self):
         # check that we indeed waited for all jobs
         self.assertGreater(time.monotonic() - t_start, 0.9)
 
+    @support.requires_gil_enabled("gh-118413: test is flaky with GIL disabled")
     def test_release_task_refs(self):
         # Issue #29861: task arguments and results should not be kept
         # alive after we are done with them.