message: Throw error when attempting to access BTC recovery explorer url
  The explorer is permanently down so attempting to make requests using
  this URL would fail anyway. Better to fail sooner than later.
  Ticket:
diff: @@ -67,7 +67,8 @@ export class Btc extends AbstractUtxoCoin {
  }
  recoveryBlockchainExplorerUrl(url: string): string {
  - return common.Environments[this.bitgo.getEnv()].smartBitApiBaseUrl + '/blockchain' + url;
  + // TODO: BG-23161 - replace smartbit block explorer which is now permanently down
  + throw new Error('btc recovery under maintenance');
  }
  getAddressInfoFromExplorer(addressBase58: string): Bluebird<any> {
  