update CHANGELOG

Author: ffakenz

CHANGELOG.md

@@ -10,7 +10,7 @@ changes.
 
 ## [0.21.0] - UNRELEASED
 
-- Use sqlite database instead of file based storage
+- Use sqlite database with event log rotation instead of file based storage
 
 - New metric for counting the number of active peers: `hydra_head_peers_connected`
 - **BREAKING** Switch to using `etcd` internally to establish a reliable L2 network