[Spanner] update spec helper #create_singers_albums_database use/exercise #create_database sample
[Spanner] update spec helper #create_singers_albums_database use/exercise #create_database sample

GoogleCloudPlatform/ruby-docs-samples,GoogleCloudPlatform/ruby-docs-samples,GoogleCloudPlatform/ruby-docs-samples,GoogleCloudPlatform/ruby-docs-samples