Bump socket.io-parser from 3.3.2 to 3.3.3 in /backend

Bumps [socket.io-parser](https://github.com/socketio/socket.io-parser) from 3.3.2 to 3.3.3.
- [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@3.3.2...3.3.3)

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

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