parseHTMLUnsafe has only one parameter (#47272)
Document.parseHTMLUnsafe has only one parameter. A future extension wants to add an options bag to parseHTMLUnsafe, which conflicts with this usage.
Note the references below, which are all consistent in parseHTMLUnsafe not having a second parameter.
This is probably a left-over from adapting the test from DOMParser.parseFromString, which does have a second string parameter, because parseFromString supports different document types.
References:
Spec: https://dom.spec.whatwg.org/#interface-document
MDN: https://developer.mozilla.org/en-US/docs/Web/API/Document/parseHTMLUnsafe_static
Blink IDL: https://source.chromium.org/chromium/chromium/src/+/main:third_party/blink/renderer/core/dom/document.idl;l=84
Firefox IDL: https://searchfox.org/mozilla-central/source/dom/webidl/Document.webidl#154
WebKit IDL: https://github.com/WebKit/WebKit/blob/main/Source/WebCore/dom/Document.idl#L44