GH-89369: test_contextlib_async finalizes event loop after each test (GH-93074)

Use asyncio.run().
(cherry picked from commit d2ef66a10be1250b13c32fbf3c0f9a9d2d98b124)

Co-authored-by: Kumar Aditya <59607654+kumaraditya303@users.noreply.github.com>