History's `scrollRestoration` steps refer to undefined node navigable

[AtkinsSJ]

What is the issue with the HTML Standard?

The scrollRestoration getter and setter steps both refer to "this's node navigable", but as far as I can tell History does not have one.

Further down in delta traverse the relevant global object's associated document's node navigable is used. I'm guessing that should be what scrollRestoration refers to as well.

Pinging @domenic as #11204 is what led me to notice this.