♻️(react) update stories for themes

The stories do not need CunninghamProvider anymore since it is
handled by the configuration for the themes support. Some stories
were also using wrong colors that didn't handle multiple themes.

packages/react/src/components/Forms/Input/index.stories.tsx

@@ -163,7 +163,7 @@ export const Controlled = () => {
   const [value, setValue] = React.useState("I am controlled");
   return (
     <div>
-      <div>
+      <div className="clr-greyscale-900">
         Value: <span>{value}</span>
       </div>
       <Input