NO-SNOW: remove unused connection _connected flag (#2627)

Author: sfc-gh-fpawlowski

src/snowflake/connector/aio/_connection.py

@@ -149,7 +149,6 @@ def __init__(
         if "platform_detection_timeout_seconds" not in kwargs:
             self._platform_detection_timeout_seconds = 0.0
 
-        self._connected = False
         self.expired = False
         # check SNOW-1218851 for long term improvement plan to refactor ocsp code
         atexit.register(self._close_at_exit)