fix(docs): replace {} with JSON.stringify({}) in custom send-sms edge function (#33794)

fix(docs): replace {} with JSON.stringify({})

apps/docs/content/guides/auth/auth-hooks/send-sms-hook.mdx

@@ -494,7 +494,7 @@ Deno.serve(async (req) => {
       )
     }
     return new Response(
-      {},
+      JSON.stringify({}),
       {
         status: 200,
         headers: {