gh-96478: Fix new test when run in refleak mode (GH-96615)

./python.exe -m test -R : test.test_typing would fail, apparently
because the dictionary used in the @patch decorator was modified.
(cherry picked from commit f0d9136c69b4ed32bfb3096f926da098623a7072)

Co-authored-by: Jelle Zijlstra <jelle.zijlstra@gmail.com>