[java-alloydb-connectors]: no grpc- modules, and no client code

Want to check if this is intentional.
This module does not have any grpc- modules, even though java-alloydb-connectors/.OwlBot-hermetic.yaml does have copy rules for them.

More strangely, the main client module [google-cloud-alloydb-connectors](https://github.com/googleapis/google-cloud-java/tree/main/java-alloydb-connectors/google-cloud-alloydb-connectors) is empty, only a pom.xml in the dir.