[scroll-animations] Out of date references to HTML spec for the event loop

[lilles]

The numbered references to the HTML spec in https://drafts.csswg.org/scroll-animations/#event-loop no longer matches

[lilles]

I was generating an older version of the HTML spec to see which steps are actually referred to, and the stale timeline update happens after resizeObserver steps with a clarifying note, but that does not match the Chromium implementation:

Note: We check for layout changes after dispatching any ResizeObservers intentionally to take programmatically sized elements into account.