Bumps the terraform group in /terraform/gcp/modules/sigstore with 1 update: [hashicorp/google](https://github.com/hashicorp/terraform-provider-google).

- [Release notes](https://github.com/hashicorp/terraform-provider-google/releases)
- [Changelog](https://github.com/hashicorp/terraform-provider-google/blob/main/CHANGELOG.md)
- [Commits](hashicorp/terraform-provider-google@v5.5.0...v5.6.0)

---
updated-dependencies:
- dependency-name: hashicorp/google
  dependency-type: direct:production
  update-type: version-update:semver-minor
  dependency-group: terraform
...

Signed-off-by: dependabot[bot] <support@github.com>

Signed-off-by: Bob Callaway <bcallaway@google.com>