Update data-fetching.mdx (withastro#2854)

Co-authored-by: Yan Thomas <[email protected]>
Co-authored-by: Chris Swithinbank <[email protected]>

src/content/docs/en/guides/data-fetching.mdx

@@ -8,7 +8,7 @@ i18nReady: true
 
 ## `fetch()` in Astro
 
-All [Astro components](/en/core-concepts/astro-components/) have access to the [global `fetch()` function](https://developer.mozilla.org/en-US/docs/Web/API/fetch) in their component script to make HTTP requests to APIs. This fetch call will be executed at build time, and the data will be available to the component template for generating dynamic HTML.
+All [Astro components](/en/core-concepts/astro-components/) have access to the [global `fetch()` function](https://developer.mozilla.org/en-US/docs/Web/API/fetch) in their component script to make HTTP requests to APIs. This fetch call will be executed at build time, and the data will be available to the component template for generating dynamic HTML. If [SSR](/en/guides/server-side-rendering/) mode is enabled, any fetch calls will be executed at runtime.
 
 💡 Take advantage of [**top-level await**](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/await#top_level_await) inside of your Astro component script.