chore: remove "Signing publications" from the logging output

[vlsi]

Summary

The message was not adding much, and it was emitted during configuration phase, so it was not even aligned with the actual signing work.

Release Note

NONE

Documentation

NONE

[loosebazooka]

gotta dco it

[vlsi]

Frankly, DCO is useless since GitHub's terms of service already require that any content someone posts on GitHub must comply with the target's license: https://docs.github.com/en/site-policy/github-terms/github-terms-of-service#6-contributions-under-repository-license

See https://ben.balter.com/2018/01/02/why-you-probably-shouldnt-add-a-cla-to-your-open-source-project/#if-a-license-isnt-good-enough-for-maintainers-you-shouldnt-subject-users-to-it

Can we somehow lift DCO restriction?
I'm running into this DCO validation every time, and it does take time to re-commit and re-push

[loosebazooka]

Yeah, it's just applied across all sigstore repos. So I dunno 🤷