Hey there, since I borrowed that GitHub action for the Emacs Lisp track I had the same error today.
See Out of sync practice exercises · Issue #705 · exercism/common-lisp · GitHub and Configlet Sync · exercism/common-lisp@69bed3c · GitHub
See Fix failing configlet-sync GHA workflow by fapdash · Pull Request #271 · exercism/emacs-lisp · GitHub for my fix.
Let me know if you would accept a PR for that.