Add setExcludeFromIndexes back to vectorvalue builder

Author: cindy-peng

google-cloud-datastore/src/main/java/com/google/cloud/datastore/VectorValue.java

@@ -142,6 +142,7 @@ public static VectorValue of(List<Value<Double>> values) {
   /** Returns a builder for {@code VectorValue} objects. */
   public static Builder newBuilder() {
     Builder builder = new VectorValue.Builder();
+    builder.setExcludeFromIndexes(true);
     builder.setMeaning(VECTOR_MEANING);
     return builder;
   }