Fix shutdown error chaning the dict during the iteration.

extensions/positron-python/python_files/positron/positron_ipykernel/connections.py

@@ -342,7 +342,7 @@ def shutdown(self):
         """
         Closes all comms and runs the `disconnect` callback.
         """
-        for comm_id in self.comms.keys():
+        for comm_id in list(self.comms.keys()):
             self._close_connection(comm_id)
 
         self.comms = {}  # implicitly deleting comms