Updating layer page

[Rumyra]

Summary

As per this issue #9656 the spec has been updated and so updating this page to reflect

Also updated one example to fall in line.

Related issues

Fixes #9656

Metadata

• Adds a new document
• Rewrites (or significantly expands) a document
• Fixes a typo, bug, or other error

[github-actions]

Preview URLs

• https://pr12185.content.dev.mdn.mozit.cloud/en-US/docs/Web/CSS/@layer

Flaws

URL: /en-US/docs/Web/CSS/@layer
Title: @layer
on GitHub
Flaw count: 1

• bad_bcd_queries:
  • No BCD data for query: css.at-rules.layer

External URLs

URL: /en-US/docs/Web/CSS/@layer
Title: @layer
on GitHub

No new external URLs

[Rumyra]

Amazing thanks @rachelandrew 👍