Clarify routing logic config instruction (withastro#13879)

Co-authored-by: Armand Philippot <git@armand.philippot.eu>

Author: sanscontext

src/content/docs/en/guides/internationalization.mdx

@@ -24,7 +24,7 @@ You can also choose to [add your own i18n logic in addition to or instead of Ast
 
 ## Configure i18n routing
 
-Both a list of all supported languages ([`locales`](/en/reference/configuration-reference/#i18nlocales)) and a default language ([`defaultLocale`](/en/reference/configuration-reference/#i18ndefaultlocale)), which must be one of the languages listed in `locales`, need to be specified in an `i18n` configuration object. Additionally, you can configure more specific routing and fallback behavior to match your desired URLs.
+In your `i18n` configuration, specify the list of all supported languages ​​([`locales`](/en/reference/configuration-reference/#i18nlocales)) and set one of them as the default language ([`defaultLocale`](/en/reference/configuration-reference/#i18ndefaultlocale)). You can also configure more specific routing and fallback behavior to match your desired URLs.
 
 ```js title="astro.config.mjs"
 import { defineConfig } from "astro/config"