Bump socket.io-parser and socket.io in /backend

Bumps [socket.io-parser](https://github.com/socketio/socket.io-parser) to 3.4.2 and updates ancestor dependency [socket.io](https://github.com/socketio/socket.io). These dependencies need to be updated together.


Updates `socket.io-parser` from 3.1.2 to 3.4.2
- [Release notes](https://github.com/socketio/socket.io-parser/releases)
- [Changelog](https://github.com/socketio/socket.io-parser/blob/main/CHANGELOG.md)
- [Commits](socketio/socket.io-parser@3.1.2...3.4.2)

Updates `socket.io` from 2.0.4 to 2.5.0
- [Release notes](https://github.com/socketio/socket.io/releases)
- [Changelog](https://github.com/socketio/socket.io/blob/main/CHANGELOG.md)
- [Commits](socketio/socket.io@2.0.4...2.5.0)

---
updated-dependencies:
- dependency-name: socket.io-parser
  dependency-type: indirect
- dependency-name: socket.io
  dependency-type: direct:production
...

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