FN: SingleFile rule

There appears to be a false negative on the SingleFile rule

Sample: https://urlscan.io/result/951ac6c6-455d-421a-96d7-42f6dfcb1744

```html
<!DOCTYPE html> <html lang=en data-kantu=1 data-react-helmet=lang style><!--
 Page saved with SingleFile 
 url: https://metamask.io/buy-crypto/ 
 saved date: Wed Jul 20 2022 23:35:53 GMT+0100 (GMT+02:00)
```