Add comment about order when re-debouncing

lib/utils/debounce.html

@@ -52,6 +52,10 @@
       if (this.isActive()) {
         this._cancelAsync();
         this._timer = null;
+        // Canceling a debouncer removes its spot from the flush queue,
+        // so if a debouncer is manually canceled and re-debounced, it
+        // will reset its flush order (this is a very minor difference from 1.x)
+        // Re-debouncing via the `debounce` API retains the 1.x FIFO flush order
         debouncerQueue.delete(this);
       }
     }