Remove page for <menuitem> element

[queengooborg]

This PR removes the pages for the <menuitem> element. Correlates with mdn/browser-compat-data#18983.

[github-actions]

Preview URLs

• /en-US/docs/Web/API/HTMLMenuElement
• /en-US/docs/Web/API/HTML_DOM_API

Flaws (7)

URL: /en-US/docs/Web/API/HTMLMenuElement
Title: HTMLMenuElement
Flaw count: 1

• macros:
  • /en-US/docs/Web/API/HTMLMenuElement/HTMLMenuElement does not exist

---

URL: /en-US/docs/Web/API/HTML_DOM_API
Title: The HTML DOM API
Flaw count: 6

• macros:
  • /en-US/docs/Web/API/HTMLDirectoryElement does not exist
  • /en-US/docs/Web/API/HTMLFrameElement does not exist
  • /en-US/docs/Web/API/HTMLIsIndexElement does not exist
  • /en-US/docs/Web/API/External does not exist
  • /en-US/docs/Web/API/ApplicationCache does not exist
  • and 1 more flaws omitted

[estelle]

I don't feel 100% comfortable removing the element page for <menuitem>.

While the element has been deprecated, we generally don't remove deprecated HTML elements, I don't think.
Also, there is a menuitem role in ARIA, along with a checkbox and radio.

Unlike <marquee>, though, this element was only ever supported in FF, and support has been removed.

We sure?

[queengooborg]

We do if no browser supports it within the last two years of releases (per BCD's irrelevance guidelines)! Firefox, the only browser to support this element, dropped support in 85.

[queengooborg]

Closed in favor of #24927.