Update google-cloud-storage.gemspec (#2891)
Update google-cloud-storage.gemspec (#2891)

Upgrade google-api-client to ~> 0.26 for Bucket::IamConfiguration.
quartzmo/google-cloud-ruby,dazuma/google-cloud-ruby,dazuma/google-cloud-ruby,googleapis/google-cloud-ruby,googleapis/google-cloud-ruby,quartzmo/google-cloud-ruby,dazuma/google-cloud-ruby,quartzmo/google-cloud-ruby,googleapis/google-cloud-ruby,googleapis/google-cloud-ruby,quartzmo/google-cloud-ruby,dazuma/google-cloud-ruby,dazuma/google-cloud-ruby,dazuma/google-cloud-ruby,quartzmo/google-cloud-ruby,googleapis/google-cloud-ruby,googleapis/google-cloud-ruby,blowmage/gcloud-ruby,quartzmo/google-cloud-ruby