Bump protobuf-java from 3.21.1 to 3.21.7 (#70)

Bumps [protobuf-java](https://github.com/protocolbuffers/protobuf) from 3.21.1 to 3.21.7.
- [Release notes](https://github.com/protocolbuffers/protobuf/releases)
- [Changelog](https://github.com/protocolbuffers/protobuf/blob/main/generate_changelog.py)
- [Commits](protocolbuffers/protobuf@v3.21.1...v3.21.7)

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

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

Author: dependabot[bot]

pom.xml

@@ -59,7 +59,7 @@
       <!-- netty and protobuf versions kept in sync with grpc's deps -->
       <netty-version>4.1.77.Final</netty-version>
       <netty-tcnative-version>2.0.53.Final</netty-tcnative-version>
-      <protobuf-version>3.21.1</protobuf-version>
+      <protobuf-version>3.21.7</protobuf-version>
       <gson-version>2.9.1</gson-version>
       <slf4j-version>1.7.36</slf4j-version>
       <junit-version>4.13.2</junit-version>