Balancer: remove unnecessary extra argument
The full HTML5 spec clones element attributes when they are added to
the ActiveFormattingElements list, so that when an element on that
list is later cloned and reinserted the attributes are the *original*
in an inline <script> block may have made to them since the element
no way the attributes could change during balancing and there is
thus no reason to keep extra copies of the attributes around.