code: public final void removePropertyChangeListener(PropertyChangeListener l)
      {
          if (sealed) onSealedMutation();
          propertyListeners = Kit.removeListener(propertyListeners, l);
      }
docs: Remove an object from the list of objects registered to receive
  notification of changes to a bounded property
  @see java.beans.PropertyChangeEvent
  @see #addPropertyChangeListener(java.beans.PropertyChangeListener)
  @param l the listener