Bump pb.version from 3.10.0 to 3.11.1 in /engine

Bumps `pb.version` from 3.10.0 to 3.11.1.

Updates `protobuf-java` from 3.10.0 to 3.11.1
- [Release notes](https://github.com/protocolbuffers/protobuf/releases)
- [Changelog](https://github.com/protocolbuffers/protobuf/blob/master/generate_changelog.py)
- [Commits](protocolbuffers/protobuf@v3.10.0...v3.11.1)

Updates `protobuf-java-util` from 3.10.0 to 3.11.1
- [Release notes](https://github.com/protocolbuffers/protobuf/releases)
- [Changelog](https://github.com/protocolbuffers/protobuf/blob/master/generate_changelog.py)
- [Commits](protocolbuffers/protobuf@v3.10.0...v3.11.1)

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

engine/pom.xml

@@ -19,7 +19,7 @@ xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xs
     UTF-8</project.build.sourceEncoding>
     <java.version>1.8</java.version>
     <grpc.version>1.25.0</grpc.version>
-    <pb.version>3.10.0</pb.version>
+    <pb.version>3.11.1</pb.version>
     <micrometer.version>1.3.0</micrometer.version>
     <start-class>io.seldon.engine.App</start-class>
     <jaeger.version>1.0.0</jaeger.version>