Update index.adoc

Author: NataliaIvakina

modules/ROOT/pages/clustering/index.adoc

@@ -16,6 +16,7 @@ This chapter describes the following:
 ** xref:clustering/setup/encryption.adoc[Intra-cluster encryption] -- How to secure the cluster communication.
 * xref:clustering/servers.adoc[Managing servers in a cluster] -- How to manage the servers in a cluster.
 * xref:clustering/databases.adoc[Managing databases in a cluster] -- How to manage the databases in a cluster.
+* xref:clustering/unbind-system-database.adoc[Unbind the `system` database] -- How to use the `neo4j-admin dbms unbind-system-db` command.
 * Monitoring -- Monitoring of a cluster.
 ** xref:clustering/monitoring/show-servers-monitoring.adoc[Monitor servers] -- The tools available for monitoring the servers in a cluster.
 ** xref:clustering/monitoring/show-databases-monitoring.adoc[Monitor databases] -- The tools available for monitoring the databases in a cluster.