docs: delete the 'In Svelte 4' redundancy in the doc. (#12908)

* Update 20-load.md

* Update 30-form-actions.md

Author: rrr63

documentation/docs/20-core-concepts/20-load.md

@@ -32,7 +32,7 @@ export function load({ params }) {
 <div>{@html data.post.content}</div>
 ```
 
-> [!LEGACY] In Svelte 4
+> [!LEGACY]
 > In Svelte 4, you'd use `export let data` instead
 
 Thanks to the generated `$types` module, we get full type safety.

documentation/docs/20-core-concepts/30-form-actions.md

@@ -151,7 +151,7 @@ export const actions = {
 {/if}
 ```
 
-> [!LEGACY] In Svelte 4
+> [!LEGACY]
 > In Svelte 4, you'd use `export let data` and `export let form` instead to declare properties
 
 ### Validation errors