message: Add changelog entries for cleanups
diff: @@ -12,10 +12,26 @@ is based on [Keep a Changelog](https://keepachangelog.com).
  destructor of the promise now checks for this case.
  - Accessing URI fields now always returns the normalized string.
  +### Changed
  +
  +- Remote spawning of actors is no longer considered experimental.
  +
  ### Deprecated
  - The obsolete meta-programming utilities `replies_to` and `reacts_to` no longer
  serve any purpose and are thus deprecated.
  +- The types `caf::byte`, `caf::optional` and `caf::string_view` became obsolete
  + after switching to C++17. Consequently, these types are now deprecated in
  + favor of their standard library counterpart.
  +
  +### Removed
  +
  +- The template type `caf::variant` also became obsolete when switching to C++17.
  + Unfortunately, the implementation was not as standalone as its deprecated
  + companions and some of the free functions like `holds_alternative` were too
  + greedy and did not play nicely with ADL when using `std::variant` in the same
  + code base. Since fixing `caf::variant` does not seem to be worth the time
  + investment, we remove this type without a deprecation cycle.
  ## [0.18.6]
  