Fix the name of neo4j-admin server unbind cmd (#2558) (#2560)

Author: NataliaIvakina

modules/ROOT/pages/clustering/servers.adoc

@@ -120,7 +120,7 @@ Once dropped, a server cannot rejoin a cluster.
 
 [NOTE]
 ====
-The same physical hardware can rejoin the cluster, provided the Neo4j installation has been "reset" (either re-installing, or running `neo4j-admin unbind`), causing it to receive a new generated server ID on next startup.
+The same physical hardware can rejoin the cluster, provided the Neo4j installation has been "reset" (either re-installing, or running `neo4j-admin server unbind`), causing it to receive a new generated server ID on next startup.
 ====
 
 == Listing servers