CHANGELOG-3.4: fix grammar, clarify WAL directory change

Signed-off-by: Gyuho Lee <gyuhox@gmail.com>

CHANGELOG-3.4.md

@@ -200,7 +200,8 @@ See [security doc](https://github.com/coreos/etcd/blob/master/Documentation/op-g
   - Again, etcd `Lease` is meant for short-periodic keepalives or sessions, in the range of seconds or minutes. Not for hours or days!
 - Enable etcd server [`raft.Config.CheckQuorum` when starting with `ForceNewCluster`](https://github.com/coreos/etcd/pull/9347).
 - Allow [non-WAL files in `--wal-dir` directory](https://github.com/coreos/etcd/pull/9743).
-  - Previously, existing files such as [`lost+found`](https://github.com/coreos/etcd/issues/7287) in WAL directory prevents etcd server boot.
+  - Previously, existing files such as [`lost+found`](https://github.com/coreos/etcd/issues/7287) in WAL directory prevent etcd server boot.
+  - Now, WAL directory that contains only `lost+found` or a file that's not suffixed with `.wal` is considered non-initialized.
 
 ### API