Fix ParentFieldMapperTests failure.

Author: jpountz

core/src/test/java/org/elasticsearch/index/mapper/ParentFieldMapperTests.java

@@ -180,7 +180,7 @@ public void testUpdateEagerGlobalOrds() throws IOException {
         String childMapping = XContentFactory.jsonBuilder().startObject().startObject("child_type")
                 .startObject("_parent").field("type", "parent_type").endObject()
                 .endObject().endObject().string();
-        IndexService indexService = createIndex("test", Settings.builder().put("index.version.created", Version.V_5_6_0).build());
+        IndexService indexService = createIndex("test");
         indexService.mapperService().merge("parent_type", new CompressedXContent(parentMapping), MergeReason.MAPPING_UPDATE, false);
         indexService.mapperService().merge("child_type", new CompressedXContent(childMapping), MergeReason.MAPPING_UPDATE, false);