don't block local echo for m.replace anymore!

src/models/room.js

@@ -1078,10 +1078,6 @@ Room.prototype._addLiveEvent = function(event, duplicateStrategy) {
  * unique transaction id.
  */
 Room.prototype.addPendingEvent = function(event, txnId) {
-    if (event.isRelation("m.replace")) {
-        return;
-    }
-
     if (event.status !== EventStatus.SENDING) {
         throw new Error("addPendingEvent called on an event with status " +
                         event.status);