Bump google-cloud-firestore from 2.20.1 to 2.20.2

Bumps [google-cloud-firestore](https://github.com/googleapis/python-firestore) from 2.20.1 to 2.20.2.
- [Release notes](https://github.com/googleapis/python-firestore/releases)
- [Changelog](https://github.com/googleapis/python-firestore/blob/main/CHANGELOG.md)
- [Commits](googleapis/python-firestore@v2.20.1...v2.20.2)

---
updated-dependencies:
- dependency-name: google-cloud-firestore
  dependency-version: 2.20.2
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

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

Author: dependabot[bot]