message: update bitgo-utxo-lib version to work on prod
  Summary:
  Reviewers: mark, alex, mtoda, bigly, tyler
  Subscribers: tyler
diff: "bigi": "1.4.0",
  "bignumber.js": "~4.0.2",
  "bitcoinjs-message": "~2.0.0",
  - "bitgo-utxo-lib": "git+https://github.com/BitGo/bitgo-utxo-lib.git#648a6cf9bf7dc883803fc962cccee641baac7f49",
  + "bitgo-utxo-lib": "git+https://github.com/BitGo/bitgo-utxo-lib.git#2a71e6af83672c8d380e8868fbc819697cd59170",
  "bluebird": "~3.5.0",
  "body-parser": "~1.18.2",
  "bs58": "2.0.1",
  