Update AdSense Management API samples to V1.2.

Reviewed in https://codereview.appspot.com/7305086/.
diff --git a/samples/adsense/sample_utils.py b/samples/adsense/sample_utils.py
index 25bd3e9..1a03399 100644
--- a/samples/adsense/sample_utils.py
+++ b/samples/adsense/sample_utils.py
@@ -100,7 +100,7 @@
   """Retrieves an AdSense Management API service via the discovery service."""
 
   # Construct a service object via the discovery service.
-  service = build("adsense", "v1.1", http=http)
+  service = build("adsense", "v1.2", http=http)
   return service