Bump websockets from 8.1 to 9.1

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] <support@github.com>

requirements.txt

@@ -39,5 +39,5 @@ txaio==20.4.1
 urllib3==1.25.10
 uvicorn==0.11.8
 uvloop==0.14.0
-websockets==8.1
+websockets==9.1
 zope.interface==5.1.0