Apply suggestions from code review

Co-authored-by: Sarah Rainsberger <5098874+sarah11918@users.noreply.github.com>

Author: florian-lefebvre

src/content/docs/en/guides/upgrade-to/v6.mdx

@@ -283,7 +283,7 @@ const integration = () => {
 
 <SourcePR number="14462" title="feat: clean deprecated APIs"/>
 
-In Astro 4.0, the `app.render()` signature allowing to pass `routeData` and `locals` as optional arguments was deprecated in favor of a single optional `renderOptions` argument.
+In Astro 4.0, the `app.render()` signature that allowed passing `routeData` and `locals` as optional arguments was deprecated in favor of a single optional `renderOptions` argument.
 
 Astro 6.0 removes this signature entirely.
 
@@ -302,13 +302,13 @@ app.render(request, { routeData, locals })
 
 <SourcePR number="14462" title="feat: clean deprecated APIs"/>
 
-In Astro 4.0, the `handleForms` prop of the `<ClientRouter />` component was deprecated.
+In Astro 4.0, the `handleForms` prop of the `<ClientRouter />` component was deprecated, as it was no longer necessary to opt in to handling `submit` events for `form` elements. This functionality has been built-in by default and the property, if still included in your project, silently had no impact on form submission.
 
-Astro 6.0 removes this prop entirely, as it had no impact on form submission anymore.
+Astro 6.0 removes this prop entirely and it now must be removed to avoid errors in your project.
 
 #### What should I do?
 
-Remove the `handleForms` property from your `<ClientRouter />` component. It is no longer necessary.
+Remove the `handleForms` property from your `<ClientRouter />` component if it exists. It has provided no additional functionality, and so removing it should not change any behavior in your project:
 
 ```astro title="src/pages/index.astro" del="handleForms"
 ---
@@ -330,13 +330,15 @@ import { ClientRouter } from "astro:transitions";
 
 <SourcePR number="14462" title="feat: clean deprecated APIs"/>
 
-In Astro 4.8.4, the `with` option of the programmatic `prefetch()` function was deprecated.
+In Astro 4.8.4, the `with` option of the programmatic `prefetch()` function was deprecated in favor of a more sensible default behavior that no longer required specifying the priority of prefetching for each page.
 
-Astro 6.0 removes this option entirely, defaulting to `link` preloading.
+Astro 6.0 removes this option entirely and it is no longer possible to configure the priority of prefetching by passing the `with` option. Attempting to do so will now cause errors.
+
+By default, Astro's prefetching now uses an automatic approach that will always try to use `<link rel="prefetch>` if supported, or will fall back to `fetch()`.
 
 #### What should I do?
 
-Review your `prefetch()` calls and remove the `with` option:
+Review your `prefetch()` calls and remove the `with` option if it still exists:
 
 ```ts
 prefetch('/about', { with: 'fetch' });