Migrate from `grpc` to `@grpc/grpc-js`

[Vessel9817]

When installing the Node modules in the example directories:

npm warn deprecated grpc@1.24.11: This library will not receive further updates other than security fixes. We recommend using @grpc/grpc-js instead.

[Vessel9817]

grpc is also a dependency of condor-framework, so we'll either need to find a replacement, or fork and update it. I'm quite fond of not forking every project I require.