How do I remove app specific passwords?

See the following from Using app-specific passwords - Apple Support

At any given time, you can have up to 25 active app-specific passwords. If you need to, you can revoke passwords individually or all at once.

1. Sign in to your Apple ID account page.
2. In the Security section, click Edit.
3. In the App Specific Passwords section, click View History.
4. Click  next to a password you want to delete, or Revoke All.

After you revoke a password, the app using that password will be signed out of your account until you generate a new password and sign in again.

Any time you change or reset your primary Apple ID password, all of your app-specific passwords are revoked automatically to protect the security of your account. You'll need to generate new app-specific passwords for any apps that you want to continue using.