build(deps): bump github.com/sigstore/rekor in /tools

Bumps [github.com/sigstore/rekor](https://github.com/sigstore/rekor) from 1.3.6 to 1.5.0.
- [Release notes](https://github.com/sigstore/rekor/releases)
- [Changelog](https://github.com/sigstore/rekor/blob/main/CHANGELOG.md)
- [Commits](sigstore/rekor@v1.3.6...v1.5.0)

---
updated-dependencies:
- dependency-name: github.com/sigstore/rekor
  dependency-version: 1.5.0
  dependency-type: indirect
...

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Author: dependabot[bot]