Bump websockets from 8.1 to 9.1 in /examples/server/asgi

Bumps [websockets](https://github.com/aaugustin/websockets) from 8.1 to 9.1.
- [Release notes](https://github.com/aaugustin/websockets/releases)
- [Changelog](https://github.com/aaugustin/websockets/blob/9.1/docs/changelog.rst)
- [Commits](https://github.com/aaugustin/websockets/compare/8.1...9.1)

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

Signed-off-by: dependabot[bot] <[email protected]>

examples/server/asgi/requirements.txt

@@ -5,4 +5,4 @@ python-engineio
 python_socketio
 uvicorn==0.13.1
 uvloop==0.14.0
-websockets==8.1
+websockets==9.1