message: Fix BTG testnet inheritance
diff: @@ -91,9 +91,8 @@ class BitcoinGoldTestnet extends Testnet implements UtxoNetwork {
  scriptHash = 0xc4;
  wif = 0xef;
  - // fields "inherited" from the Bitcoin mainnet
  - messagePrefix = Bitcoin.prototype.messagePrefix;
  - family = Bitcoin.prototype.family;
  + messagePrefix = BitcoinGold.prototype.messagePrefix;
  + family = BitcoinGold.prototype.family;
  }
  class Litecoin extends Mainnet implements UtxoNetwork {
  