Fix readPref in replication docs.

Author: behackett

source/applications/replication.txt

@@ -206,7 +206,7 @@ connecting to the :term:`replica set` that provides each :term:`shard`
 in the cluster.
 
 In the :program:`mongo` shell, use the
-:method:`readPreference() <cursor.readPreference()>` cursor method
+:method:`readPref() <cursor.readPref()>` cursor method
 provides access to read preferences.
 
 .. warning::