Bug 1815430 - Remove another chunk of dead code that I forgot to commit. a=bustage

MANUAL PUSH: Bustage fix CLOSED TREE

accessible/xul/XULListboxAccessible.cpp

@@ -381,22 +381,6 @@ bool XULListboxAccessible::AreItemsOperable() const {
 }
 
 LocalAccessible* XULListboxAccessible::ContainerWidget() const {
-  if (IsAutoCompletePopup() && mContent->GetParent()) {
-    // This works for XUL autocompletes. It doesn't work for HTML forms
-    // autocomplete because of potential crossprocess calls (when autocomplete
-    // lives in content process while popup lives in chrome process). If that's
-    // a problem then rethink Widgets interface.
-    nsCOMPtr<nsIDOMXULMenuListElement> menuListElm =
-        mContent->GetParent()->AsElement()->AsXULMenuList();
-    if (menuListElm) {
-      RefPtr<mozilla::dom::Element> inputElm;
-      menuListElm->GetInputField(getter_AddRefs(inputElm));
-      if (inputElm) {
-        LocalAccessible* input = mDoc->GetAccessible(inputElm);
-        return input ? input->ContainerWidget() : nullptr;
-      }
-    }
-  }
   return nullptr;
 }