Fix ApigeeEnvironment update response type. (GoogleCloudPlatform#12415)

Author: masich

mmv1/products/apigee/Environment.yaml

@@ -35,7 +35,7 @@ timeouts:
   delete_minutes: 30
 autogen_async: true
 async:
-  actions: ['create', 'delete', 'update']
+  actions: ['create', 'delete']
   type: 'OpAsync'
   operation:
     base_url: '{{op_id}}'