message: fix upgrade command
diff: @@ -9,7 +9,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/).
  ## [1.4.1] - 2021-12-27
  ### Fixed
  -- Upgrade command must be run with `--unstable` flag.
  +- Upgrade errors due unstable features.
  ## [1.4.0] - 2021-12-27
  This version of Lume has a big internal code refactor but maintaining the public API,
  