Bump firebase-tools from 13.14.2 to 13.16.0 in /functions

Bumps [firebase-tools](https://github.com/firebase/firebase-tools) from 13.14.2 to 13.16.0.
- [Release notes](https://github.com/firebase/firebase-tools/releases)
- [Changelog](https://github.com/firebase/firebase-tools/blob/master/CHANGELOG.md)
- [Commits](firebase/firebase-tools@v13.14.2...v13.16.0)

---
updated-dependencies:
- dependency-name: firebase-tools
  dependency-type: direct:development
  update-type: version-update:semver-minor
...

Signed-off-by: dependabot[bot] <[email protected]>