gh-150257: Skip test_free_threading.test_pickle

Skip test_pickle_dumps_with_concurrent_dict_mutation() of
test_free_threading.test_pickle for now, since pickle.dumps(dict) has
a race condition causing an unfinite loop.

Author: vstinner

Lib/test/test_free_threading/test_pickle.py

@@ -8,6 +8,8 @@
 @threading_helper.requires_working_threading()
 class TestPickleFreeThreading(unittest.TestCase):
 
+    @unittest.skip("gh-150257: pickle.dumps(dict) has a race condition "
+                   "causing an unfinite loop")
     def test_pickle_dumps_with_concurrent_dict_mutation(self):
         # gh-146452: Pickling a dict while another thread mutates it
         # used to segfault. batch_dict_exact() iterated dict items via