helpers.async_bulk to return explicit tuple.

in Python3.11, when <stats_only> is False, it returns a tuple of (<success>, <errors>)
insted of only list of <errors>.
The fix makes sure that it returns a tuple when <stats_only> is True
and list otherwise.

Author: BhaaVast

elasticsearch/_async/helpers.py

@@ -345,7 +345,7 @@ async def async_bulk(
         else:
             success += 1
 
-    return success, failed if stats_only else errors
+    return (success, failed) if stats_only else errors
 
 
 async def async_scan(