build(deps): bump @google-cloud/storage in /functions

Bumps [@google-cloud/storage](https://github.com/googleapis/nodejs-storage) from 6.2.2 to 7.15.2.
- [Release notes](https://github.com/googleapis/nodejs-storage/releases)
- [Changelog](https://github.com/googleapis/nodejs-storage/blob/main/CHANGELOG.md)
- [Commits](googleapis/nodejs-storage@v6.2.2...v7.15.2)

---
updated-dependencies:
- dependency-name: "@google-cloud/storage"
  dependency-type: direct:production
  update-type: version-update:semver-major
...

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Author: dependabot[bot]