CHANGELOG-3.4: highlight embed.Config.LogOutput field change

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

CHANGELOG-3.4.md

@@ -71,6 +71,7 @@ See [code changes](https://github.com/coreos/etcd/compare/v3.3.0...v3.4.0) and [
   - Previously, `Create(dirpath string, metadata []byte) (*WAL, error)`, now `Create(lg *zap.Logger, dirpath string, metadata []byte) (*WAL, error)`.
 - Remove [`embed.Config.SetupLogging`](https://github.com/coreos/etcd/pull/9572).
   - Now logger is set up automatically based on [`embed.Config.Logger`, `embed.Config.LogOutput`, `embed.Config.Debug` fields](https://github.com/coreos/etcd/pull/9572).
+- Change [`embed.Config.LogOutput` type from `string` to `[]string`](https://github.com/coreos/etcd/pull/9579) to support multiple log outputs.
 - Remove [`pkg/cors` package](https://github.com/coreos/etcd/pull/9490).
 - Move `"github.com/coreos/etcd/snap"` to [`"github.com/coreos/etcd/raftsnap"`](https://github.com/coreos/etcd/pull/9211).
 - Move `"github.com/coreos/etcd/etcdserver/auth"` to [`"github.com/coreos/etcd/etcdserver/v2auth"`](https://github.com/coreos/etcd/pull/9275).