Bump ws from 8.7.0 to 8.8.1 in /backend

Bumps [ws](https://github.com/websockets/ws) from 8.7.0 to 8.8.1.
- [Release notes](https://github.com/websockets/ws/releases)
- [Commits](websockets/ws@8.7.0...8.8.1)

---
updated-dependencies:
- dependency-name: ws
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

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Author: dependabot[bot]