Bump protobuf-java from 3.11.4 to 3.16.3 in /java/showcase

Bumps [protobuf-java](https://github.com/protocolbuffers/protobuf) from 3.11.4 to 3.16.3.
- [Release notes](https://github.com/protocolbuffers/protobuf/releases)
- [Changelog](https://github.com/protocolbuffers/protobuf/blob/main/generate_changelog.py)
- [Commits](https://github.com/protocolbuffers/protobuf/compare/v3.11.4...v3.16.3)

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

Signed-off-by: dependabot[bot] <support@github.com>
diff --git a/java/showcase/pom.xml b/java/showcase/pom.xml
index 5c2b951..8e725d5 100644
--- a/java/showcase/pom.xml
+++ b/java/showcase/pom.xml
@@ -48,7 +48,7 @@
         <dependency>
             <groupId>com.google.protobuf</groupId>
             <artifactId>protobuf-java</artifactId>
-            <version>3.11.4</version>
+            <version>3.16.3</version>
         </dependency>
 
         <!-- Undertow web server -->