[v4] Namespace override syntax is not valid CSS

[malobre]

I'm using a CSS formatter (biome) that won't parse --font-* because it is not a valid ident-token according to https://drafts.csswg.org/css-syntax-3/#ident-token-diagram

I see two possibilities:

• Keep the current syntax:
  In this case we should also support the escaped version (which is valid CSS syntax), e.g: --font-\*: initial;.
• Change the syntax:
  The simplest alternative would be to drop the asterisk, e.g --font: initial;.