Update mplex changelog.

Roman S. Borschel · Roman S. Borschel · commit d5793fed37cc · 2020-10-13T17:59:27.000+02:00
diff --git a/muxers/mplex/CHANGELOG.md b/muxers/mplex/CHANGELOG.md
@@ -1,5 +1,8 @@
 # 0.23.0 [unreleased]
 
+- Split receive buffers per substream.
+  [PR 1784](https://github.com/libp2p/rust-libp2p/pull/1784).
+
 - Address a potential stall when reading from substreams.
 
 - Send a `Reset` or `Close` to the remote when a substream is dropped,
