fix line numbers

Author: kentcdodds

exercises/09.sync-external/README.mdx

@@ -13,7 +13,7 @@ the geolocation API. The geolocation API is not a part of React, so we need to
 synchronize the external state of the geolocation API with the internal state of
 our component.
 
-```tsx lines=31-35
+```tsx lines=25-28
 import { useSyncExternalStore } from 'react'
 
 type LocationData =