Adds dependency on google-cloud bom (#1034)
Adds dependency on google-cloud bom (#1034)

* Depend on shaded spanner

* Use google-cloud bom

GoogleCloudPlatform/java-docs-samples,GoogleCloudPlatform/java-docs-samples,GoogleCloudPlatform/java-docs-samples,GoogleCloudPlatform/java-docs-samples,GoogleCloudPlatform/java-docs-samples,GoogleCloudPlatform/java-docs-samples