Bump com.google.cloud:google-cloud-firestore in /modules/gcloud

Bumps [com.google.cloud:google-cloud-firestore](https://github.com/googleapis/java-firestore) from 3.8.1 to 3.9.3.
- [Release notes](https://github.com/googleapis/java-firestore/releases)
- [Changelog](https://github.com/googleapis/java-firestore/blob/main/CHANGELOG.md)
- [Commits](googleapis/java-firestore@v3.8.1...v3.9.3)

---
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] <[email protected]>

Author: dependabot[bot]

modules/gcloud/build.gradle

@@ -4,7 +4,7 @@ dependencies {
     api project(':testcontainers')
 
     testImplementation 'com.google.cloud:google-cloud-datastore:2.14.2'
-    testImplementation 'com.google.cloud:google-cloud-firestore:3.8.1'
+    testImplementation 'com.google.cloud:google-cloud-firestore:3.9.3'
     testImplementation 'com.google.cloud:google-cloud-pubsub:1.123.8'
     testImplementation 'com.google.cloud:google-cloud-spanner:6.36.1'
     testImplementation 'com.google.cloud:google-cloud-bigtable:2.20.3'