[docs] Fix useMutation hook name

Author: x0k

apps/docs/src/content/docs/integrations/generic-backend.mdx

@@ -9,7 +9,7 @@ import { Card, Code } from '@astrojs/starlight/components'
 import Form from './_generic-backend.svelte';
 import formCode from './_generic-backend.svelte?raw';
 
-You can improve the experience of sending data to the server by using the `useAction` hook.
+You can improve the experience of sending data to the server by using the `useMutation` hook.
 
 <Code code={formCode} lang="svelte" />