Unlinks an identity from a user by deleting it. The user will no longer be able to sign in with that identity once it's unlinked.
unlinkIdentity()
.The user identity to unlink.
// retrieve all identites linked to a user
final identities = await supabase.auth.getUserIdentities();
// find the google identity
final googleIdentity = identities.firstWhere(
(element) => element.provider == 'google',
);
// unlink the google identity
await supabase.auth.unlinkIdentity(googleIdentity);