Revert "pythonGH-124639: add back loop param to staggered_race (python#124700)"

This reverts commit e0a41a5.

Author: ZeroIntensity

Lib/asyncio/staggered.py

@@ -11,7 +11,7 @@
 class _Done(Exception):
     pass
 
-async def staggered_race(coro_fns, delay, *, loop=None):
+async def staggered_race(coro_fns, delay):
     """Run coroutines with staggered start times and take the first to finish.
 
     This method takes an iterable of coroutine functions. The first one is
@@ -82,13 +82,7 @@ async def run_one_coro(this_index, coro_fn, this_failed):
             raise _Done
 
     try:
-        tg = taskgroups.TaskGroup()
-        # Intentionally override the loop in the TaskGroup to avoid
-        # using the running loop, preserving backwards compatibility
-        # TaskGroup only starts using `_loop` after `__aenter__`
-        # so overriding it here is safe.
-        tg._loop = loop
-        async with tg:
+        async with taskgroups.TaskGroup() as tg:
             for this_index, coro_fn in enumerate(coro_fns):
                 this_failed = locks.Event()
                 exceptions.append(None)

Lib/test/test_asyncio/test_staggered.py

@@ -121,25 +121,6 @@ async def coro(index):
         self.assertIsInstance(excs[0], ValueError)
         self.assertIsNone(excs[1])
 
-    def test_loop_argument(self):
-        loop = asyncio.new_event_loop()
-        async def coro():
-            self.assertEqual(loop, asyncio.get_running_loop())
-            return 'coro'
-
-        async def main():
-            winner, index, excs = await staggered_race(
-                [coro],
-                delay=0.1,
-                loop=loop
-            )
-
-            self.assertEqual(winner, 'coro')
-            self.assertEqual(index, 0)
-
-        loop.run_until_complete(main())
-        loop.close()
-
 
 if __name__ == "__main__":
     unittest.main()