message: Clarify changelog text
diff: ## [1.38.3] - 2021-12-14
  ### Added
  -- Added inheritance structure for Autodesk Standard Surface versions 1.0.0 and 1.0.1.
  +- Added an inheritance structure for versions of Autodesk Standard Surface.
  - Added versioning and customization support to MaterialX namespaces in C++.
  - Added preprocessor definitions for the API version to MaterialXCore.
  - Added color transform methods to the Image class.
  