docs: update readme

Author: thorbrink

README.md

@@ -231,8 +231,6 @@ card?.style.setProperty('--c-card--color--surface', '#1f2937');
   - Every consumed token must be listed in the component token manifest.
   - Companion tokens such as `-border` and `-alt` must be declared in global tokens and referenced explicitly.
   - Shadow internals (`shadow-color`, `shadow-amount`) must be listed directly.
-- **Extras support**:
-  - `tokens.create($prefix, $tokens, $extras)` supports computed extras.
 
 ### Architectural Limitations (important)