Revert "docs: fix Prop interface type error in example (#2191)" (#2200)

This reverts commit dd57dce.

Author: bencodezen

src/guide/typescript/composition-api.md

@@ -40,14 +40,12 @@ You can use either type-based declaration OR runtime declaration, but you cannot
 We can also move the props types into a separate interface:
 
 ```vue
-<script lang="ts">
+<script setup lang="ts">
 interface Props {
   foo: string
   bar?: number
 }
-</script>
 
-<script setup lang="ts">
 const props = defineProps<Props>()
 </script>
 ```