Documentation: Fix the Elasticsearch shards/replicas link

Replace the broken shards/replicas link with the currently working one.

Change-Id: Ie5abd681e29c49b3d12a772458812eb0ef93d55c
diff --git a/Documentation/config-gerrit.txt b/Documentation/config-gerrit.txt
index 1e68b04..77d18db 100644
--- a/Documentation/config-gerrit.txt
+++ b/Documentation/config-gerrit.txt
@@ -2927,7 +2927,7 @@
 [[elasticsearch.numberOfShards]]elasticsearch.numberOfShards::
 +
 Sets the number of shards to use per index. Refer to the
-link:https://www.elastic.co/guide/en/elasticsearch/reference/current/_basic_concepts.html#getting-started-shards-and-replicas[
+link:https://www.elastic.co/guide/en/elasticsearch/reference/current/getting-started-concepts.html#getting-started-shards-and-replicas[
 Elasticsearch documentation] for details.
 +
 Defaults to 5.
@@ -2935,7 +2935,7 @@
 [[elasticsearch.numberOfReplicas]]elasticsearch.numberOfReplicas::
 +
 Sets the number of replicas to use per index. Refer to the
-link:https://www.elastic.co/guide/en/elasticsearch/reference/current/_basic_concepts.html#getting-started-shards-and-replicas[
+link:https://www.elastic.co/guide/en/elasticsearch/reference/current/getting-started-concepts.html#getting-started-shards-and-replicas[
 Elasticsearch documentation] for details.
 +
 Defaults to 1.