:seedling: Bump github.com/sigstore/fulcio from 1.8.5 to 1.8.6 (#2793)

Bumps [github.com/sigstore/fulcio](https://github.com/sigstore/fulcio) from 1.8.5 to 1.8.6.
- [Release notes](https://github.com/sigstore/fulcio/releases)
- [Changelog](https://github.com/sigstore/fulcio/blob/main/CHANGELOG.md)
- [Commits](https://github.com/sigstore/fulcio/compare/v1.8.5...v1.8.6)

---
updated-dependencies:
- dependency-name: github.com/sigstore/fulcio
  dependency-version: 1.8.6
  dependency-type: indirect
...

Signed-off-by: dependabot[bot] <support@github.com>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>