Bump github.com/sigstore/cosign from 1.13.1 to 1.13.6

Bumps [github.com/sigstore/cosign](https://github.com/sigstore/cosign) from 1.13.1 to 1.13.6.
- [Release notes](https://github.com/sigstore/cosign/releases)
- [Changelog](https://github.com/sigstore/cosign/blob/main/CHANGELOG.md)
- [Commits](sigstore/cosign@v1.13.1...v1.13.6)

---
updated-dependencies:
- dependency-name: github.com/sigstore/cosign
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

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