Bump @grpc/grpc-js from 1.9.13 to 1.9.15 (#1573)

Bumps [@grpc/grpc-js](https://github.com/grpc/grpc-node) from 1.9.13 to 1.9.15. - [Release notes](https://github.com/grpc/grpc-node/releases) - [Commits](https://github.com/grpc/grpc-node/compare/@grpc/grpc-js@1.9.13...@grpc/grpc-js@1.9.15) --- updated-dependencies: - dependency-name: "@grpc/grpc-js" dependency-type: indirect ... Signed-off-by: dependabot[bot] <support@github.com> Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com> Co-authored-by: Daniel Lee <danielylee@google.com>

Author: dependabot[bot]