Update example backup-transport resource overlay

Make sure that the example overlay for configuring a product's
default-active backup transport names the latest incarnation.

Change-Id: I867062f703d3b5f39d40736805ba15f0d21b1afd

overlays/backup/frameworks/base/packages/SettingsProvider/res/values/defaults.xml

@@ -17,5 +17,5 @@
  */
 -->
 <resources>
-    <string name="def_backup_transport">com.google.android.backup/.BackupTransportService</string>
+    <string name="def_backup_transport">com.google.android.gms/.backup.BackupTransportService</string>
 </resources>