gh-150175: Add correctly formatted news entry

Author: saisneha196

Misc/NEWS.d/next/Library/2026-05-21-11-25-58.gh-issue-150175.8H4Caz.rst

@@ -0,0 +1,4 @@
+Fix race condition in :class:`unittest.mock.ThreadingMock` where concurrent
+calls could lose increments to ``call_count`` and other attributes. Fixed by
+overriding ``_increment_mock_call`` in
+:class:`~unittest.mock.ThreadingMixin` with the existing lock.