Update source/includes/fact-replica-set-sync-from-is-temporary.rst

The last of these options is v2.4 only.  Not 100% sure how to report this in the "right" way, but we should note it.

Signed-off-by: Sam Kleinman <[email protected]>

Author: Greg Studer

source/includes/fact-replica-set-sync-from-is-temporary.rst

@@ -5,8 +5,9 @@ temporary override of default behavior. If:
 
 - the connection to the sync target closes, or 
 
-- the sync target falls more than 30 seconds behind another member of
-  the replica set;
+- .. versionchanged:: 2.4
+     The sync target falls more than 30 seconds behind another member of
+     the replica set; 
 
 then, the :program:`mongod` instant will revert to the default sync
 logic and target.