Update APIs to use new Google cloud paths.

common/gcloud/pubsub/quota.go

 // Copyright 2015 The LUCI Authors. All rights reserved.
 // Use of this source code is governed under the Apache License, Version 2.0
 // that can be found in the LICENSE file.
 
 package pubsub
 
 import (
         "time"
 
-        "google.golang.org/cloud/pubsub"
+        "cloud.google.com/go/pubsub"
 )
 
 // Cloud PubSub quota is documented here:
 // https://cloud.google.com/pubsub/quotas
 const (
         // MaxPublishSize is the maximum size, in bytes, of the published message
         // (10 MB).
         //
         // See: https://cloud.google.com/pubsub/publisher
         MaxPublishSize = 10 * 1024 * 1024
 
         // MaxPublishBatchSize is the maximum PubSub batch size.
         MaxPublishBatchSize = pubsub.MaxPublishBatchSize
 
         // MaxProjectMessagesPerSecond is the maximum number of requests per second,
         // across the entire project.
         MaxProjectMessagesPerSecond = 10000
 
         // MaxSubscriptionPullSize is the maximum number of subscription records that
         // can be pulled at a time.
         MaxSubscriptionPullSize = pubsub.DefaultMaxPrefetch
 
         // MaxACKDeadline is the maximum acknowledgement deadline that can be applied
         // to a leased subscription Message.
         MaxACKDeadline = 600 * time.Second
 )