Replace deprecation with warning in hgroup

[hamishwillee]

This changes the deprecation at top of the hgroup to a warning note. The reason is that while the API should not be used until it properly supports assistive technologies, it is still in at least some formal specifications and not officially deprecated (and as such there is a mismatch with browser compatibility data too). This follows on from discussed in #2902 (comment)

I have not removed the tag "Deprecated" from hgroup which means that it is still listed in HTML elements reference > Obsolete and deprecated elements. That is technically incorrect, but I still don't want to promote it's use.

Note that when/if this is really deprecated we should do a much more thorough tagging exercise as mention of hgroup is scattered through the docs (e.g. anywhere we list that the

[github-actions]

Preview URLs

• https://pr4977.content.dev.mdn.mozit.cloud/en-US/docs/Web/HTML/Element
• https://pr4977.content.dev.mdn.mozit.cloud/en-US/docs/Web/HTML/Element/hgroup
• https://pr4977.content.dev.mdn.mozit.cloud/en-US/docs/Web/Guide/HTML/Content_categories

Flaws

None! 🎉

External URLs

URL: /en-US/docs/Web/HTML/Element
Title: HTML elements reference
on GitHub

No new external URLs

---

URL: /en-US/docs/Web/HTML/Element/hgroup
Title: <hgroup>
on GitHub

No new external URLs

---

URL: /en-US/docs/Web/Guide/HTML/Content_categories
Title: Content categories
on GitHub

• https://html.spec.whatwg.org/multipage/dom.html (1 time) (Note! This may be a new URL 👀)

(this comment was updated 2021-05-14 08:03:25.125274)

[chrisdavidmills]

Nice work @hamishwillee . I've done a few small copy edits, but this is ready to merge now.