Bumps [Google.Protobuf](https://github.com/protocolbuffers/protobuf) from 3.15.5 to 3.15.6. - [Release notes](https://github.com/protocolbuffers/protobuf/releases) - [Changelog](https://github.com/protocolbuffers/protobuf/blob/master/generate_changelog.py) - [Commits](https://github.com/protocolbuffers/protobuf/compare/v3.15.5...v3.15.6) Signed-off-by: dependabot-preview[bot] <support@dependabot.com> Co-authored-by: dependabot-preview[bot] <27856297+dependabot-preview[bot]@users.noreply.github.com>pull/3136/head