Fix scribblehub. Again

[fake-name]

So the dev here is being a real PITA.

Failing to pass a referrer = immediate 403, possibly for long periods of time (3 days?). If you're behind CGNAT, it seems to be possible to do testing at least.

Should fix #3059 + #2983

[gamebeaker]

@fake-name you copied the code of walkTocPages from parser.js

wouldn't it suffice to call:

            await HttpClient.setDeclarativeNetRequestRules(
                ScribblehubParser.makeFetchRules(this.tocURL)
            );

Before calling walkTocPages. (That would prevent code duplicates)