ElasticContainer: Upgrade V6_8 to elasticsearch 6.8.12

Change-Id: I0946c39dac2fb36878bc1bfe41675d5f4bdc5d0d
diff --git a/javatests/com/google/gerrit/elasticsearch/ElasticContainer.java b/javatests/com/google/gerrit/elasticsearch/ElasticContainer.java
index 60bf64c..1a43269 100644
--- a/javatests/com/google/gerrit/elasticsearch/ElasticContainer.java
+++ b/javatests/com/google/gerrit/elasticsearch/ElasticContainer.java
@@ -41,7 +41,7 @@
       case V6_7:
         return "blacktop/elasticsearch:6.7.2";
       case V6_8:
-        return "blacktop/elasticsearch:6.8.11";
+        return "blacktop/elasticsearch:6.8.12";
       case V7_0:
         return "blacktop/elasticsearch:7.0.1";
       case V7_1: