docs(vue): streamline usage example with script setup syntax

Author: treighmawaka

static/usage/v8/input/theming/colors/vue.md

@@ -11,12 +11,7 @@
   <ion-input aria-label="Dark input" color="dark" placeholder="Dark input"></ion-input>
 </template>
 
-<script lang="ts">
+<script setup lang="ts">
   import { IonInput } from '@ionic/vue';
-  import { defineComponent } from 'vue';
-
-  export default defineComponent({
-    components: { IonInput },
-  });
 </script>
 ```