Hello,
Registering a provider simply allows your app to start using App Check with that provider. It means App Check is ready to accept attestations from that provider. It won't actually have any effect until you include the App Check SDKs into your app and start sending traffic. There is generally no need to unregister an attestation provider.
In your case, the SafetyNet provider is showing as registered, which means App Check is ready to accept SafetyNet attestations for that app (because you have already entered your SHA-256 certificate fingerprint) and its API is enabled. But this does not actually have any effect until you include the App Check SDK into your app and start making SafetyNet attestations.
Hope that helps.
Victor