Migrate UITextField to use iOS 13 delegate method

[mindgraffiti]

When we no longer support iOS 12 in the apps, migrate the UITextFields in Authenticator to use the new textFieldDidChangeSelection: method and remove the workarounds found in the project. Example PR, where an IBAction was attached directly to the UITextField because the delegate method can't be used.

[mokagio]

As of 2025/02/06 this repo is a public archive and no longer under development.

If you think this issue is still relevant for one or both of the former clients, please open an issue in WordPress/Jetpack iOS and WooCommerce iOS

Thanks!