Update websockets requirement from ==12.* to ==13.* in /server (#229)

Updates the requirements on [websockets](https://github.com/python-websockets/websockets) to permit the latest version.
- [Release notes](https://github.com/python-websockets/websockets/releases)
- [Commits](python-websockets/websockets@12.0...13.0)

---
updated-dependencies:
- dependency-name: websockets
  dependency-type: direct:production
...

server/requirements.txt

@@ -31,7 +31,7 @@ reportlab==4.2.*
 requests==2.31.*
 sentry-sdk==2.14.*
 tqdm==4.66.*
-websockets==12.*
+websockets==13.*
 
 # deploy
 psycopg2==2.9.9