docs: move fetchContentNavigation into function (#1403)

Author: nobkd

docs/content/4.api/2.composables/2.fetch-content-navigation.md

@@ -16,7 +16,7 @@ content/
 
 ```vue [app.vue]
 <script setup>
-const { data: navigation } = await useAsyncData('navigation', fetchContentNavigation())
+const { data: navigation } = await useAsyncData('navigation', () => fetchContentNavigation())
 </script>
 
 <template>