Bump Google.Protobuf from 3.12.3 to 3.12.4 (#4529)
Bump Google.Protobuf from 3.12.3 to 3.12.4 (#4529)

Bumps [Google.Protobuf](https://github.com/protocolbuffers/protobuf) from 3.12.3 to 3.12.4.
- [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/v3.12.3...v3.12.4)

Signed-off-by: dependabot-preview[bot] <5bdcd3c0d4d24ae3e71b3b452a024c6324c7e4bb@dependabot.com>

Co-authored-by: dependabot-preview[bot] <6a4c1c4838f800d1998274cd5234e1f65c55e90c@users.noreply.github.com>
simonlaroche/akka.net,simonlaroche/akka.net