chore: add missing space between two strings joined in logger.warn().

src/module.ts

@@ -746,7 +746,7 @@ export default defineNuxtModule<ModuleOptions>({
               logger.warn([
                 'Using `<NuxtLayout>` inside `app.vue` will cause unwanted layout shifting in your application.',
                 'Consider removing `<NuxtLayout>` from `app.vue` and using it in your pages.'
-              ].join(''))
+              ].join(' '))
             }
           }
         })