♻️(react) update token.ts to handles themes

Some components were using wrong design tokens and this was noticed
only when changing themes, like using hard-coded "white" instead of
"greyscale-000".

packages/react/src/components/Forms/Checkbox/tokens.ts

@@ -2,7 +2,7 @@ import { DefaultTokens } from "@openfun/cunningham-tokens";
 
 export const tokens = (defaults: DefaultTokens) => ({
   "background-color--hover": defaults.theme.colors["greyscale-200"],
-  "background-color": "white",
+  "background-color": defaults.theme.colors["greyscale-000"],
   "font-size": defaults.theme.font.sizes.m,
   "font-weight": defaults.theme.font.weights.medium,
   color: defaults.theme.colors["greyscale-900"],