[resize-observer] Referred step from HTML Processing Model should now be 16

[Loirooriol]

https://drafts.csswg.org/resize-observer/#integrations

ResizeObserver processing happens inside the step 7.12 of the HTML Processing Model event loop.
Step 12 is currently underspecified as:
"For each fully active Document in docs, update the rendering or user interface of that Document and its browsing context to reflect the current state.".

But looking at https://html.spec.whatwg.org/multipage/webappapis.html#update-the-rendering, this is now step 16

16. For each fully active Document in docs, update the rendering or user interface of that Document and its browsing context to reflect the current state.