Fix update loop should not disconnect causing race condition

When starting the client, on phone migrations, it would
disconnect twice right after connecting which would
trigger a not-connected error.

telethon/client/updates.py

@@ -218,7 +218,6 @@ class UpdateMethods(UserMethods):
             except asyncio.TimeoutError:
                 pass
             except asyncio.CancelledError:
-                self.disconnect()
                 return
             except Exception as e:
                 continue  # Any disconnected exception should be ignored