deleteAccount method
Implementation
Future<void> deleteAccount(String? pubKey) async {
_deleteKeyPair(pubKey);
final mnemonics = Map.of(_storage.encryptedMnemonics.val);
mnemonics.removeWhere((key, _) => key == pubKey);
_storage.encryptedMnemonics.val = mnemonics;
final seeds = Map.of(_storage.encryptedRawSeeds.val);
seeds.removeWhere((key, _) => key == pubKey);
_storage.encryptedRawSeeds.val = seeds;
}