Update CommentsList.ascx.cs

We had a serious memory leak on our project and tracked it down to the CommentsList sublayout.  As mentioned in the note, when subscribing to an event in on_load it is important to unsubscribe in the dispose() method or else garbage collection will have trouble deallocating the memory for this control.

Fixing memory leak by unsubscribing from event in the Dispose() method.
http://adeneys.wordpress.com/2009/02/24/warning-memory-leaks-ahead/