Issue with the "Secrets" doc

[Daneage]

I found an issue with this document.

Title: Secrets
Location: https://fly.io/docs/js/the-basics/secrets/
Source: https://github.com/superfly/docs/blob/main/js/the-basics/secrets.html.md

Describe the issue

This command is no longer correct, please update document.
"The '<' operator is reserved for future use."

Additional info