Update cloud-sdk image

emulators tags is light compared to latest

Author: eddumelendez

testcontainers/google/pubsub.py

@@ -27,14 +27,14 @@ class PubSubContainer(DockerContainer):
     ::
 
         def test_docker_run_pubsub():
-            config = PubSubContainer('google/cloud-sdk:latest')
+            config = PubSubContainer('google/cloud-sdk:emulators')
             with config as pubsub:
                 publisher = pubsub.get_publisher()
                 topic_path = publisher.topic_path(pubsub.project, "my-topic")
                 topic = publisher.create_topic(topic_path)
     """
 
-    def __init__(self, image="google/cloud-sdk:latest",
+    def __init__(self, image="google/cloud-sdk:emulators",
                  project="test-project", port=8432, **kwargs):
         super(PubSubContainer, self).__init__(image=image, **kwargs)
         self.project = project