Bump protobuf-java from 3.9.1 to 3.16.1 in /other/java/client

Bumps [protobuf-java](https://github.com/protocolbuffers/protobuf) from 3.9.1 to 3.16.1.
- [Release notes](https://github.com/protocolbuffers/protobuf/releases)
- [Changelog](https://github.com/protocolbuffers/protobuf/blob/master/generate_changelog.py)
- [Commits](https://github.com/protocolbuffers/protobuf/compare/v3.9.1...v3.16.1)

---
updated-dependencies:
- dependency-name: com.google.protobuf:protobuf-java
  dependency-type: direct:production
...

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

other/java/client/pom.xml

@@ -14,7 +14,7 @@
     </parent>
 
     <properties>
-        <protobuf.version>3.9.1</protobuf.version>
+        <protobuf.version>3.16.1</protobuf.version>
         <!-- follow https://github.com/grpc/grpc-java -->
         <grpc.version>1.23.0</grpc.version>
         <guava.version>30.0-jre</guava.version>