Bump protobuf.version from 3.19.1 to 3.21.5

Bumps `protobuf.version` from 3.19.1 to 3.21.5.

Updates `protobuf-java` from 3.19.1 to 3.21.5
- [Release notes](https://github.com/protocolbuffers/protobuf/releases)
- [Changelog](https://github.com/protocolbuffers/protobuf/blob/main/generate_changelog.py)
- [Commits](protocolbuffers/protobuf@v3.19.1...v3.21.5)

Updates `protobuf-java-util` from 3.19.1 to 3.21.5

---
updated-dependencies:
- dependency-name: com.google.protobuf:protobuf-java
  dependency-type: direct:production
  update-type: version-update:semver-minor
- dependency-name: com.google.protobuf:protobuf-java-util
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

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

pom.xml

@@ -20,7 +20,7 @@
         <!-- name of parameter changed in latest mvn javadoc plugin version-->
         <additionalOptions>-Xdoclint:none</additionalOptions>
         <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
-        <protobuf.version>3.19.1</protobuf.version>
+        <protobuf.version>3.21.5</protobuf.version>
         <testcontainers.version>1.16.2</testcontainers.version>
         <kafka-libs.version>6.1.4</kafka-libs.version>
     </properties>