[Backend Dependencies Update] Update flask-socketio to 4.3.1

[pyup-bot]

This PR updates flask-socketio from 4.2.1 to 4.3.1.

Changelog

4.3.1

- fix is_connected in test client ([commit](https://github.com/miguelgrinberg/flask-socketio/commit/0d2f041dc0e7cd976860c2d2c9fb163bd20f5460))

4.3.0

- Handle callbacks for emits outside of request context [1054](https://github.com/miguelgrinberg/flask-socketio/issues/1054) ([commit](https://github.com/miguelgrinberg/flask-socketio/commit/1bd15e05b75aaf94dacd4f24af44601b76d300a9))
- Improve test client unit test to use two concurrent clients ([commit](https://github.com/miguelgrinberg/flask-socketio/commit/2c6b07d0419f2b6e03554c32e42a91cf963c6d6d))
- Accept skip_sid argument in emit[1147](https://github.com/miguelgrinberg/flask-socketio/issues/1147) ([commit](https://github.com/miguelgrinberg/flask-socketio/commit/c06e78e78de3d10f9009bf778ad188bf3f4945ed))
- Fix is_connected() method in test client (Fixes https://github.com/miguelgrinberg/python-socketio/issues/385) ([commit](https://github.com/miguelgrinberg/flask-socketio/commit/a05ff51344654aef00b8dc0fce8028500d380b05))
- Log warning when gevent is used but WebSocket is missing [1140](https://github.com/miguelgrinberg/flask-socketio/issues/1140) ([commit](https://github.com/miguelgrinberg/flask-socketio/commit/15ad45a6b90362bc1b73b6a7b0fa6781c6b98b05)) (thanks **Eric Rodrigues Pires**!)
- More accurate logging documentation ([commit](https://github.com/miguelgrinberg/flask-socketio/commit/255d3d6b41b4f22736d2798a8f70264334eb3173))

Links

• PyPI: https://pypi.org/project/flask-socketio
• Changelog: https://pyup.io/changelogs/flask-socketio/
• Repo: http://github.com/miguelgrinberg/Flask-SocketIO/
• Docs: https://pythonhosted.org/Flask-SocketIO/

[pyup-bot]

Closing this in favor of #929