Bump protobuf-java from 3.20.1 to 3.21.0 (#52)

Bumps [protobuf-java](https://github.com/protocolbuffers/protobuf) from 3.20.1 to 3.21.0.
- [Release notes](https://github.com/protocolbuffers/protobuf/releases)
- [Changelog](https://github.com/protocolbuffers/protobuf/blob/main/generate_changelog.py)
- [Commits](protocolbuffers/protobuf@v3.20.1...v3.21.0)

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

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Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

pom.xml

@@ -254,7 +254,7 @@
         <dependency>
             <groupId>com.google.protobuf</groupId>
             <artifactId>protobuf-java</artifactId>
-            <version>3.20.1</version>
+            <version>3.21.0</version>
         </dependency>
         <!-- tests -->
         <dependency>