Disable the trailing throttle event in the editing session heartbeat

Throttle sends an event as soon as the function is called. Then
we wait X minutes, but we only want to send another event if
there's any activity *after* those X minutes.

services/web/public/coffee/main/event.coffee

@@ -44,7 +44,7 @@ define [
 						"X-CSRF-Token": window.csrfToken
 					}
 				})
-			, EDIT_SESSION_HEARTBEAT_INTERVAL)
+			, EDIT_SESSION_HEARTBEAT_INTERVAL, trailing: false)
 
 
 			sendMB: (key, segmentation = {}) ->