Bump @grpc/grpc-js version to ^1.7.1

[antonstefer]

See this issue: grpc/grpc-node#2231

Leaving the version constraint at ^1.7.0 would already install 1.7.1 in a clean project. In real world projects resolving peer dependencies could still result in the old slow version. Therefore I would like the dependency to be pinned to ^1.7.1