Bump protobuf-maven-plugin from 0.5.1 to 0.6.1
Bump protobuf-maven-plugin from 0.5.1 to 0.6.1

Bumps [protobuf-maven-plugin](https://github.com/xolstice/protobuf-maven-plugin) from 0.5.1 to 0.6.1.
- [Release notes](https://github.com/xolstice/protobuf-maven-plugin/releases)
- [Changelog](https://github.com/xolstice/protobuf-maven-plugin/blob/protobuf-maven-plugin-0.6.1/release-pom.xml)
- [Commits](https://github.com/xolstice/protobuf-maven-plugin/compare/protobuf-maven-plugin-0.5.1...protobuf-maven-plugin-0.6.1)

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

Fixes #735

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Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=326533316

google/truth,google/truth,google/truth