Update use-notification-center.md for invalid directory

[hashirshoaeb]

while using

import { useNotificationCenter } from "react-toastify/addons/useNotificationCenter"

i was getting the following error.

Cannot find module 'react-toastify/addons/useNotificationCenter' or its corresponding type declarations.

When i google i got this article: https://blog.logrocket.com/using-react-toastify-style-toast-messages

And found the difference in imports i.e file name. So this PR is the fix for that.