Excluded a property from the index (#270)

* Excluded a property from the index

For doc purposes

* Update Concepts.java

Author: WalterHub

datastore/src/main/java/com/google/datastore/snippets/Concepts.java

@@ -210,7 +210,8 @@ public void testProperties() {
         .set("done", false)
         .set("priority", 4)
         .set("percent_complete", 10.0)
-        .set("description", "Learn Cloud Datastore")
+        .set("description",
+          StringValue.builder("Learn Cloud Datastore").excludeFromIndexes(true).build())
         .build();
     // [END properties]
     assertValidEntity(task);