build(deps-dev): bump google/protobuf from 3.14.0 to 3.15.1
build(deps-dev): bump google/protobuf from 3.14.0 to 3.15.1

Bumps [google/protobuf](https://github.com/protocolbuffers/protobuf-php) from 3.14.0 to 3.15.1.
- [Release notes](https://github.com/protocolbuffers/protobuf-php/releases)
- [Commits](https://github.com/protocolbuffers/protobuf-php/compare/v3.14.0...v3.15.1)

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