[3.11] GH-109067: fix randomly failing `test_async_gen_asyncio_gc_aclose_09` test (GH-109142) (#109150)

GH-109067: fix randomly failing `test_async_gen_asyncio_gc_aclose_09` test (GH-109142)

Use `asyncio.sleep(0)` instead of short sleeps.
(cherry picked from commit ccd48623d4860e730a16f3f252d67bfea8c1e905)

Co-authored-by: Kumar Aditya <kumaraditya@python.org>