[css-transitions-2] Drop no-longer-relevant comment about generating transitions via script

Author: birtles

css-transitions-2/Overview.bs

@@ -101,9 +101,6 @@ The <dfn>owning element</dfn> of a transition refers to the element or
 pseudo-element to which the 'transition-property' property was applied that
 generated the animation.
 
-If a transition was generated directly by script then it has no <a>owning
-element</a>.
-
 If a transition generated using the markup defined in this specification is
 later disassociated from that markup because it is cancelled or replaced by
 a newer transition, the animation is disassociated from its <a>owning