docs: remove unnecessary indent (#3092)

Co-authored-by: noah.choi <[email protected]>

website/pages/docs/theming/usage.mdx

@@ -48,7 +48,7 @@ The `token()` function is useful when you need to provide a fallback value. The
 
   </Tab>
   <Tab>
-   ```js
+    ```js
     import { css } from '../styled-system/css'
 
     const className = css({ border: '1px solid {colors.red.400}' })