ElasticVersionTest#version6: Add missing test for V6_4

Change-Id: I4ca4f304cdff6d8275e60856b992ee32d9c61027
diff --git a/gerrit-elasticsearch/src/test/java/com/google/gerrit/elasticsearch/ElasticVersionTest.java b/gerrit-elasticsearch/src/test/java/com/google/gerrit/elasticsearch/ElasticVersionTest.java
index 9e89114..ec4add4 100644
--- a/gerrit-elasticsearch/src/test/java/com/google/gerrit/elasticsearch/ElasticVersionTest.java
+++ b/gerrit-elasticsearch/src/test/java/com/google/gerrit/elasticsearch/ElasticVersionTest.java
@@ -54,6 +54,7 @@
   public void version6() throws Exception {
     assertThat(ElasticVersion.V6_2.isV6()).isTrue();
     assertThat(ElasticVersion.V6_3.isV6()).isTrue();
+    assertThat(ElasticVersion.V6_4.isV6()).isTrue();
     assertThat(ElasticVersion.V5_6.isV6()).isFalse();
   }
 }