cassandra/cluster.py: make asyncio default insted of asyncore

since python 3.12 is deprecating asyncore, we should make
asyncio the default fallback event loop.

now that it's fixed and we verified it's working in multiple
python versions we support (from 3.8 - 3.12)

Author: fruch

cassandra/cluster.py

@@ -139,7 +139,7 @@ def _is_gevent_monkey_patched():
     try:
         from cassandra.io.libevreactor import LibevConnection as DefaultConnection  # NOQA
     except ImportError:
-        from cassandra.io.asyncorereactor import AsyncoreConnection as DefaultConnection  # NOQA
+        from cassandra.io.asyncioreactor import AsyncioConnection as DefaultConnection  # NOQA
 
 # Forces load of utf8 encoding module to avoid deadlock that occurs
 # if code that is being imported tries to import the module in a seperate