fix: remove unused variable in Lib/asyncio/streams.py

Signed-off-by: yihong0618 <zouzou0208@gmail.com>

Author: yihong0618

Lib/asyncio/streams.py

@@ -214,7 +214,6 @@ def _stream_reader(self):
         return self._stream_reader_wr()
 
     def _replace_transport(self, transport):
-        loop = self._loop
         self._transport = transport
         self._over_ssl = transport.get_extra_info('sslcontext') is not None