docs: reorder document-driven page slots components description

Author: AnaelBonnafous

docs/content/3.guide/1.writing/7.document-driven.md

@@ -62,6 +62,8 @@ To do so, you only have to create a component with the same name in your project
 
 - `<DocumentDrivenNotFound />`{lang=html}
 
+This component will be shown when no page has been found for the current URL.
+
 ```html [components/DocumentDrivenNotFound.vue]
 <template>
   <h1>Page not found</h1>
@@ -78,8 +80,6 @@ This component will be shown when there is no content for the current page, but
 </template>
 ```
 
-This component will be shown when no page has been found for the current URL.
-
 ## Layout binding
 
 As the page data is available beforehand, the layout can be defined in the page front-matter: