How do you stop hide my email

See the "How do you deactivate or delete an email address with Hide My Email" section in the support document you posted from.

Once deactivated, you would need to log in to the website you used it for, and change the email address to your actual email address.

Some websites will require you update your password too. As the Sign in with Apple feature, does not use one. But it will depend on the specific website in that case.