message: bump version in changelog - austin already did package/lock
diff: @@ -7,6 +7,10 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
  ## Unreleased
  +## 5.3.1 - 2021-01-07
  +
  +### Changed
  +
  - Class `XrpIssuedCurrency` has been renamed to `XrplIssuedCurrency`.
  ## 5.3.0 - 2020-11-17
  