vendor: update all dependencies

vendor/cloud.google.com/go/cloud.go

@@ -12,9 +12,29 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
-// Package cloud is the root of the packages used to access Google Cloud
-// Services. See https://godoc.org/cloud.google.com/go for a full list
-// of sub-packages.
-//
-// This package documents how to authorize and authenticate the sub packages.
+/*
+Package cloud is the root of the packages used to access Google Cloud
+Services. See https://godoc.org/cloud.google.com/go for a full list
+of sub-packages.
+
+Examples in this package show ways to authorize and authenticate the
+sub packages.
+
+Connection Pooling
+
+Connection pooling differs in clients based on their transport. Cloud
+clients either rely on HTTP or gRPC transports to communicate
+with Google Cloud.
+
+Cloud clients that use HTTP (bigquery, compute, storage, and translate) rely on the
+underlying HTTP transport to cache connections for later re-use. These are cached to
+the default http.MaxIdleConns and http.MaxIdleConnsPerHost settings in
+http.DefaultTransport.
+
+For gPRC clients (all others in this repo), connection pooling is configurable. Users
+of cloud client libraries may specify option.WithGRPCConnectionPool(n) as a client
+option to NewClient calls. This configures the underlying gRPC connections to be
+pooled and addressed in a round robin fashion.
+
+*/
 package cloud // import "cloud.google.com/go"