[3.12] GH-109067: fix randomly failing test_async_gen_asyncio_gc_aclose_09 test (GH-109142) (#109149)

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 ccd4862)

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

Author: miss-islington

Lib/test/test_asyncgen.py

@@ -1057,8 +1057,7 @@ async def gen():
                 while True:
                     yield 1
             finally:
-                await asyncio.sleep(0.01)
-                await asyncio.sleep(0.01)
+                await asyncio.sleep(0)
                 DONE = 1
 
         async def run():
@@ -1068,7 +1067,10 @@ async def run():
             del g
             gc_collect()  # For PyPy or other GCs.
 
-            await asyncio.sleep(0.1)
+            # Starts running the aclose task
+            await asyncio.sleep(0)
+            # For asyncio.sleep(0) in finally block
+            await asyncio.sleep(0)
 
         self.loop.run_until_complete(run())
         self.assertEqual(DONE, 1)