Remove Headers.getAll()

[ddbeck]

Headers.getAll() has been removed from browsers for over two years. Consequently, it's being removed from BCD. This PR:

• Redirects getAll() to get() (which, in contemporary browsers, does the same thing)
• Removes all the mentions of getAll that I could find 👋

[github-actions]

Preview URLs

• https://pr8284.content.dev.mdn.mozit.cloud/en-US/docs/Mozilla/Firefox/Releases/52
• https://pr8284.content.dev.mdn.mozit.cloud/en-US/docs/Web/API/Headers
• https://pr8284.content.dev.mdn.mozit.cloud/en-US/docs/Web/API/Headers/get

Flaws

Note! 1 document with no flaws that don't need to be listed. 🎉

URL: /en-US/docs/Mozilla/Firefox/Releases/52
Title: Firefox 52 for developers
on GitHub
Flaw count: 17

• broken_links:
  • Is currently http:// but can become https://
  • Can't resolve /en-US/docs/Archive/B2G_OS/API/MozVoicemail
  • Can't resolve /en-US/docs/Archive/B2G_OS/API/MozVoicemailEvent
  • Can't resolve /en-US/docs/Archive/B2G_OS/API/MozVoicemailStatus
  • Can't resolve /en-US/docs/Archive/B2G_OS/API/Navigator/mozVoicemail
  • and 12 more flaws omitted

---

URL: /en-US/docs/Web/API/Headers
Title: Headers
on GitHub
Flaw count: 2

• macros:
  • /en-US/docs/Web/API/Headers/forEach does not exist
• bad_bcd_links:
  • no explanation!

External URLs

URL: /en-US/docs/Mozilla/Firefox/Releases/52
Title: Firefox 52 for developers
on GitHub

No new external URLs

---

URL: /en-US/docs/Web/API/Headers
Title: Headers
on GitHub

• https://fetch.spec.whatwg.org/ (1 time)

---

URL: /en-US/docs/Web/API/Headers/get
Title: Headers.get()
on GitHub

No external URLs

[teoli2003]

Thanks, Daniel! 👏