CHANGELOG: update "pkg/adt"

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

CHANGELOG-3.4.md

@@ -143,6 +143,8 @@ See [code changes](https://github.com/etcd-io/etcd/compare/v3.3.0...v3.4.0) and
   - `"github.com/coreos/etcd/snap"` to `"go.etcd.io/etcd/etcdserver/api/snap"`.
   - `"github.com/coreos/etcd/store"` to `"go.etcd.io/etcd/etcdserver/api/v2store"`.
 - 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).
 
 ### Dependency