CHANGELOG-3.4: highlight version string change

Signed-off-by: Gyuho Lee <leegyuho@amazon.com>

CHANGELOG-3.4.md

@@ -154,6 +154,8 @@ See [code changes](https://github.com/etcd-io/etcd/compare/v3.3.0...v3.4.0) and
 - Change [snapshot file permissions](https://github.com/etcd-io/etcd/pull/9977): On Linux, the snapshot file changes from readable by all (mode 0644) to readable by the user only (mode 0600).
 - Change [`pkg/adt.IntervalTree` from `struct` to `interface`](https://github.com/etcd-io/etcd/pull/10959).
   - See [`pkg/adt` README](https://github.com/etcd-io/etcd/tree/master/pkg/adt) and [`pkg/adt` godoc](https://godoc.org/go.etcd.io/etcd/pkg/adt).
+- Release branch `/version` defines version `3.4.x-pre`, instead of `3.4.y+git`.
+  - Use `3.4.5-pre`, instead of `3.4.4+git`.
 
 ### Dependency