message: Add removed metrics to changelog
diff: @@ -33,6 +33,7 @@ All notable changes to this project will be documented in this file. The format
  * Experimental, nix-based kubernetes testing support has been removed.
  * Experimental support for libp2p has been removed.
  * The `isolation_reconnect_delay` configuration, which has been ignored since 1.3, has been removed.
  +* The libp2p-exclusive metrics of `read_futures_in_flight`, `read_futures_total`, `write_futures_in_flight`, `write_futures_total` have been removed.
  