Found outdated docs - fix included

[Nilzkool]

Hi Team Supervision,

I am a big fan of your work!

I ran a deep scan of your supervision folder using a GitHub tool I've built called DeepDocs, and observed a few outdated docs like utils/boxes.md. You can see the details in this commit.

The tool is free for OSS. Just sharing in case it's helpful.

Thanks,

Nilzkool