Fix mongos warning for primaryPreferred read prefs

Author: jmikola

source/applications/replication.txt

@@ -256,8 +256,8 @@ behavior <replica-set-read-preference-behavior>`. See also the
       .. versionchanged:: 2.2
          :program:`mongos` added full support for read preferences.
 
-      When connecting to a :program:`mongos` instance older 2.2, using
-      a client that supports read preference modes,
+      When connecting to a :program:`mongos` instance older than 2.2,
+      using a client that supports read preference modes,
       :readmode:`primaryPreferred` will send queries to secondaries.
 
 .. readmode:: secondary