Update flask-socketio requirement from <6,>=5.6.1 to >=5.7.0,<6 (#4540)

Updates the requirements on [flask-socketio](https://code.miguelgrinberg.com/miguelgrinberg/flask-socketio) to permit the latest version.

---
updated-dependencies:
- dependency-name: flask-socketio
  dependency-version: 5.7.0
  dependency-type: direct:production
...

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requirements.txt

@@ -3,7 +3,7 @@ feedparser~=6.0  # For parsing RSS/Atom feeds
 flask-compress
 flask-login>=0.6.3
 flask-paginate
-flask-socketio>=5.6.1,<6 # Re #3910
+flask-socketio>=5.7.0,<6 # Re #3910
 flask>=3.1,<4
 flask_cors # For the Chrome extension to operate
 flask_restful