Remove unsupported font-family `fangsong` value

### MDN URL

https://developer.mozilla.org/en-US/docs/Web/CSS/Reference/Properties/font-family

### What specific section or headline is this issue about?

Values and Compatibility

### What information was incorrect, unhelpful, or incomplete?

The "Values" section should be updated. It should describe the generic(xxx) values listed in "Formal syntax" section. For reference, check https://drafts.csswg.org/css-fonts/#generic(fangsong)-def

The compatibility section list values such as `kai, khmer-mul, nastaliq` as supported since the beginning. But these are script specific generic font names added recently into the CSS spec draft, and at this moment, no browser support them.

### What did you expect to see?

Those issues fixed.

### Do you have any supporting links, references, or citations?

For details about the script-specific generic font names, check these links:
https://w3c.github.io/i18n-drafts/articles/typography/fontstyles.en.html
https://github.com/w3c/i18n-discuss/wiki/Generic-font-families
https://drafts.csswg.org/css-fonts/

### Do you have anything more you want to share?

_No response_

### MDN metadata

Page report details

* Folder: `en-us/web/css/reference/properties/font-family`
* MDN URL: https://developer.mozilla.org/en-US/docs/Web/CSS/Reference/Properties/font-family
* GitHub URL: https://github.com/mdn/content/blob/main/files/en-us/web/css/reference/properties/font-family/index.md
* Last commit: https://github.com/mdn/content/commit/5a8de324f0aa3873d757f68e4fcaf6bbc0104711
* Document last modified: 2025-10-31T11:25:44.000Z