build(deps-dev): bump @grpc/proto-loader from 0.7.3 to 0.7.7

Bumps [@grpc/proto-loader](https://github.com/grpc/grpc-node) from 0.7.3 to 0.7.7.
- [Release notes](https://github.com/grpc/grpc-node/releases)
- [Commits](https://github.com/grpc/grpc-node/compare/@grpc/proto-loader@0.7.3...@grpc/proto-loader@0.7.7)

---
updated-dependencies:
- dependency-name: "@grpc/proto-loader"
  dependency-type: direct:development
  update-type: version-update:semver-patch
...

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