Update with-magic example (#19207)

fixes the event argument inside the function call
- argument is `e` but `event` was used instead

examples/with-magic/pages/login.js

@@ -12,7 +12,7 @@ const Login = () => {
   const [errorMsg, setErrorMsg] = useState('')
 
   async function handleSubmit(e) {
-    event.preventDefault()
+    e.preventDefault()
 
     if (errorMsg) setErrorMsg('')