CHANGELOG: describe about user with no password

CHANGELOG-3.4.md

@@ -57,6 +57,7 @@ See [code changes](https://github.com/etcd-io/etcd/compare/v3.3.0...v3.4.0) and
 - Add [consistency check in snapshot status](https://github.com/etcd-io/etcd/pull/10109). If consistency check on snapshot file fails, `snapshot status` returns `"snapshot file integrity check failed..."` error.
 - Add [`Verify` function to perform corruption check on WAL contents](https://github.com/etcd-io/etcd/pull/10603).
 - Improve [heartbeat send failure logging](https://github.com/etcd-io/etcd/pull/10663).
+- Support [users with no password](https://github.com/etcd-io/etcd/pull/9817) for reducing security risk introduced by leaked password. The users can only be authenticated with CommonName based auth.
 
 ### Breaking Changes