Version 1.3 release.

Updates CHANGELOG, version, docs.
diff --git a/docs/dyn/pubsub_v1beta1.subscriptions.html b/docs/dyn/pubsub_v1beta1.subscriptions.html
index dbaeb5f..b7a118a 100644
--- a/docs/dyn/pubsub_v1beta1.subscriptions.html
+++ b/docs/dyn/pubsub_v1beta1.subscriptions.html
@@ -246,7 +246,7 @@
     The object takes the form of:
 
 {
-    "ackDeadlineSeconds": 42, # The new Ack deadline. Must be >= 1.
+    "ackDeadlineSeconds": 42, # The new Ack deadline. Must be >= 0.
     "ackId": "A String", # The Ack ID.
     "subscription": "A String", # The name of the subscription from which messages are being pulled.
   }