message: Document removal of obsolete test macros
diff: @@ -13,6 +13,11 @@ is based on [Keep a Changelog](https://keepachangelog.com).
  via config file or CLI to `0s` and then printing the config parameter, e.g.,
  via `--dump-config`.
  +### Removed
  +
  +- Dropped three obsolete (and broken) macros in the `unit_test.hpp` header:
  + `CAF_CHECK_FAILED`, `CAF_CHECK_FAIL` and `CAF_CHECK_PASSED`.
  +
  ## [0.18.3] - 2021-05-21
  ### Added
  