minor: typo fix

Author: Sam Kleinman

source/reference/configuration-options.txt

@@ -778,7 +778,7 @@ Sharding Cluster Options
       :setting:`configdb` setting in the same order.
 
       If your configuration databases reside in more that one data
-      center, order the hosts in the :setting:`setting` tting so
+      center, order the hosts in the :setting:`setting` setting so
       that the config database that is closest to the majority of your
       :program:`mongos` instances is first servers in the list.