Use anext in AsyncIterablePayload on Python 3.10+ (#10941)

Author: bdraco

CHANGES/10941.bugfix.rst

@@ -0,0 +1 @@
+10915.bugfix.rst

aiohttp/payload.py

@@ -810,7 +810,10 @@ async def write_with_length(
 
         try:
             while True:
-                chunk = await self._iter.__anext__()
+                if sys.version_info >= (3, 10):
+                    chunk = await anext(self._iter)
+                else:
+                    chunk = await self._iter.__anext__()
                 if remaining_bytes is None:
                     await writer.write(chunk)
                 # If we have a content length limit