Bump com.google.cloud:google-cloud-firestore from 3.20.2 to 3.21.0

Bumps [com.google.cloud:google-cloud-firestore](https://github.com/googleapis/java-firestore) from 3.20.2 to 3.21.0.
- [Release notes](https://github.com/googleapis/java-firestore/releases)
- [Changelog](https://github.com/googleapis/java-firestore/blob/main/CHANGELOG.md)
- [Commits](googleapis/java-firestore@v3.20.2...v3.21.0)

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

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

Author: dependabot[bot]

pom.xml

@@ -51,7 +51,7 @@
         <dependency>
             <groupId>com.google.cloud</groupId>
             <artifactId>google-cloud-firestore</artifactId>
-            <version>3.20.2</version>
+            <version>3.21.0</version>
             <scope>provided</scope>
         </dependency>
         <dependency>