ElasticContainer: Use Elasticsearch 6.4.1 for V6_4 tests

Change-Id: I9dec94b81079574da0c66bca2860e093f70be8f4
diff --git a/gerrit-elasticsearch/src/main/java/com/google/gerrit/elasticsearch/testing/ElasticContainer.java b/gerrit-elasticsearch/src/main/java/com/google/gerrit/elasticsearch/testing/ElasticContainer.java
index 3a9c7d0..b20afca 100644
--- a/gerrit-elasticsearch/src/main/java/com/google/gerrit/elasticsearch/testing/ElasticContainer.java
+++ b/gerrit-elasticsearch/src/main/java/com/google/gerrit/elasticsearch/testing/ElasticContainer.java
@@ -52,7 +52,7 @@
       case V6_3:
         return "docker.elastic.co/elasticsearch/elasticsearch-oss:6.3.2";
       case V6_4:
-        return "docker.elastic.co/elasticsearch/elasticsearch-oss:6.4.0";
+        return "docker.elastic.co/elasticsearch/elasticsearch-oss:6.4.1";
     }
     throw new IllegalStateException("No tests for version: " + version.name());
   }