Stale gRPC stubs used for cloud spanner

[carl-mastrangelo]

googleapis/google-cloud-java#2989 fails due to an old version of the generated grpc code in use. Looking on maven, it looks like 1.2.0, which is a few months old at this point. It would be nice if this could be bumped to 1.10.0

@garrettjonesgoogle would you mind taking a look?

[carl-mastrangelo]

@garrettjonesgoogle friendly ping. Any chance these could be rolled out in the near future?

[garrettjonesgoogle]

We need to change this line: https://github.com/googleapis/gapic-generator/blob/master/build.gradle#L426

[garrettjonesgoogle]

Follow-up: this has been released in google-cloud-spanner.