Bump protobuf-java from 3.15.7 to 3.15.8

Bumps [protobuf-java](https://github.com/protocolbuffers/protobuf) from 3.15.7 to 3.15.8.
- [Release notes](https://github.com/protocolbuffers/protobuf/releases)
- [Changelog](https://github.com/protocolbuffers/protobuf/blob/master/generate_changelog.py)
- [Commits](protocolbuffers/protobuf@v3.15.7...v3.15.8)

Signed-off-by: dependabot-preview[bot] <[email protected]>

Author: dependabot-preview[bot]

pom.xml

@@ -38,7 +38,7 @@
         <maven.compiler.source>1.8</maven.compiler.source>
         <maven.compiler.target>1.8</maven.compiler.target>
         <gson.version>2.8.6</gson.version>
-        <protobuf.version>3.15.7</protobuf.version>
+        <protobuf.version>3.15.8</protobuf.version>
     </properties>
 
     <modules>