[Markdown] [Web/HTML] Remove ID attributes from HTML input page

[wbamberg]

Part of #8961.

This PR removes uses of the id attribute from the main HTML <input> page: https://developer.mozilla.org/en-US/docs/Web/HTML/Element/input.

Mostly this is removing IDs like htmlattrdefthing, which are only used as targets from the preceding section. I've replaced those links with attr-thing which you get from the {{htmlattrdef}} macro.

I also took out a spurious live sample, and corrected a heading ID that didn't match the derived heading ID and was being referenced by a live sample (and so would have been broken in Markdown).

I have not removed IDs from the big table of input types in https://developer.mozilla.org/en-US/docs/Web/HTML/Element/input#input_types, which uses them for live samples. I thought this table is quite nice and not worth trying to dismember at this point. It will stay in HTML anyway.

[github-actions]

Preview URLs

• https://pr9124.content.dev.mdn.mozit.cloud/en-US/docs/Web/HTML/Element/input

Flaws

URL: /en-US/docs/Web/HTML/Element/input
Title: <input>: The Input (Form Input) element
on GitHub
Flaw count: 6

• macros:
  • /en-US/docs/Web/API/HTMLInputElement/checkValidity does not exist
  • /en-US/docs/Web/API/HTMLInputElement/setCustomValidity does not exist
  • /en-US/docs/Web/API/ValidityState/valueMissing does not exist
  • /en-US/docs/Web/API/ValidityState/valueMissing does not exist
  • /en-US/docs/Web/API/ValidityState/valid does not exist
  • and 1 more flaws omitted

External URLs

URL: /en-US/docs/Web/HTML/Element/input
Title: <input>: The Input (Form Input) element
on GitHub

No new external URLs