build(deps): bump com.google.cloud:google-cloud-spanner-hibernate-tools (GoogleCloudPlatform#3219)

Bumps [com.google.cloud:google-cloud-spanner-hibernate-tools](https://github.com/GoogleCloudPlatform/google-cloud-spanner-hibernate) from 3.8.0 to 3.9.1.
- [Release notes](https://github.com/GoogleCloudPlatform/google-cloud-spanner-hibernate/releases)
- [Changelog](https://github.com/GoogleCloudPlatform/google-cloud-spanner-hibernate/blob/master/CHANGELOG.md)
- [Commits](GoogleCloudPlatform/google-cloud-spanner-hibernate@v3.8.0...v3.9.1)

---
updated-dependencies:
- dependency-name: com.google.cloud:google-cloud-spanner-hibernate-tools
  dependency-version: 3.9.1
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

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