minor: fixing glossary link

Author: Sam Kleinman

source/administration/replica-sets.txt

@@ -171,7 +171,7 @@ other members in the set will not advertise the hidden member in the
 
    .. versionchanged:: 2.0 
 
-   For :term:`shard clusters` running with replica sets before 2.0 if
+   For :term:`sharded clusters <shard cluster>` running with replica sets before 2.0 if
    you reconfigured a member as hidden, you *had* to restart
    :program:`mongos` to prevent queries from reaching the hidden
    member.