chore: update changelog

CHANGES-5.0.md

@@ -6,6 +6,7 @@
 * Fix JWT plugin don't support non-integer timestamp claims. [#8867](https://github.com/emqx/emqx/pull/8867)
 * Avoid publishing will message when client fails to auhtenticate. [#8887](https://github.com/emqx/emqx/pull/8887)
 * Speed up dispatching of shared subscription messages in a cluster [#8893](https://github.com/emqx/emqx/pull/8893)
+* Speed up updating the configuration, When some nodes in the cluster are down. [#8857](https://github.com/emqx/emqx/pull/8857)
 
 ## Enhancements