FF90: Minor tweaks to JavaScript class private features

[hamishwillee]

Trivial docs follow up for #5386

I just reviewed the updated private class features docs for FF90. These already did pretty much everything I thought needed doing. All this does is:

1. Release note - referred to private class fields and method. Strictly accurate, but worth mentioning static methods here.
2. Fixed up a couple of link titles to "Private class fields" which has now been named private class features.

I don't think anything else "needs" to be done.

[github-actions]

Preview URLs

• https://pr6323.content.dev.mdn.mozit.cloud/en-US/docs/Mozilla/Firefox/Releases/90
• https://pr6323.content.dev.mdn.mozit.cloud/en-US/docs/Web/JavaScript/Reference/Classes

Flaws

URL: /en-US/docs/Mozilla/Firefox/Releases/90
Title: Firefox 90 for developers
on GitHub
Flaw count: 1

• macros:
  • /en-US/docs/Web/CSS/image-set() redirects to /en-US/docs/Web/CSS/image/image-set()

---

URL: /en-US/docs/Web/JavaScript/Reference/Classes
Title: Classes
on GitHub
Flaw count: 2

• bad_bcd_links:
  • no explanation!
  • no explanation!

External URLs

URL: /en-US/docs/Mozilla/Firefox/Releases/90
Title: Firefox 90 for developers
on GitHub

No new external URLs

---

URL: /en-US/docs/Web/JavaScript/Reference/Classes
Title: Classes
on GitHub

No new external URLs

[hamishwillee]

@meyerweb Nice job on the JS updates.

In the top level Classes doc it refers to private fields and to Static methods and properties. However it does not talk about private methods, or static private methods or static private fields.

Is that something we should update too?