Elasticsearch: Mention support for 6.7 from Gerrit 2.15.13

Change-Id: I17a19903e9059c3ffb6913b31ae26bfeb5f98e6f
diff --git a/pages/site/elasticsearch.md b/pages/site/elasticsearch.md
index cc2e289..7fa943b 100644
--- a/pages/site/elasticsearch.md
+++ b/pages/site/elasticsearch.md
@@ -18,6 +18,7 @@
 | 6.4.x                 | 2.14.12 or 2.15.4      |
 | 6.5.x                 | 2.15.8 or 2.16.1       |
 | 6.6.x                 | 2.15.10 or 2.16.5      |
+| 6.7.x                 | 2.15.13 or 2.16.8      |
 
 Note that although Elasticsearch 2.4.x is supported, we do not recommend using
 such an old version.