Remove atexit handler that hangs on Chromium shutdown

The server thread is daemon=True so it dies with the process.
The atexit close() calls thread.join() which hangs if Chromium
shutdown blocks.

Author: Andrew Utkin

src/py/kaleido/_sync_server.py

@@ -73,8 +73,6 @@ def open(self, *args: Any, silence_warnings=False, **kwargs: Any) -> None:
         self._task_queue: Queue[Task | None] = Queue()
         self._thread.start()
         self._initialized = True
-        close = partial(self.close, silence_warnings=True)
-        atexit.register(close)
 
     def close(self, *, silence_warnings=False):
         """Reset the singleton back to an uninitialized state."""