Bump engine.io from 6.4.1 to 6.4.2 in /fixtures/browser

Bumps [engine.io](https://github.com/socketio/engine.io) from 6.4.1 to 6.4.2.
- [Release notes](https://github.com/socketio/engine.io/releases)
- [Changelog](https://github.com/socketio/engine.io/blob/main/CHANGELOG.md)
- [Commits](socketio/engine.io@6.4.1...6.4.2)

---
updated-dependencies:
- dependency-name: engine.io
  dependency-type: indirect
...

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