docs: Fix Svelte tutorial import snippet (#18729)

The error message I receive is: "Cannot find module 'src/supabaseClient' or its corresponding type declarations." This error indicates that the TypeScript compiler is unable to locate the module I'm trying to import.

apps/docs/pages/guides/getting-started/tutorials/with-svelte.mdx

@@ -66,7 +66,7 @@ Let's set up a Svelte component to manage logins and sign ups. We'll use Magic L
 
 ```html src/lib/Auth.svelte
 <script lang="ts">
-  import { supabase } from 'src/supabaseClient'
+  import { supabase } from '../supabaseClient'
 
   let loading = false
   let email = ''