CHANGELOG: add Go 1.10+ for 3.4

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

CHANGELOG-3.4.md

@@ -47,6 +47,7 @@ See [code changes](https://github.com/coreos/etcd/compare/v3.3.0...v3.4.0) and [
   - Move `"github.com/coreos/etcd/etcdserver/auth"` to [`"github.com/coreos/etcd/etcdserver/v2auth"`](https://github.com/coreos/etcd/pull/9275).
   - Change v3 `etcdctl snapshot` exit codes with [`snapshot` package](https://github.com/coreos/etcd/pull/9118/commits/df689f4280e1cce4b9d61300be13ca604d41670a).
     - Exit on error with exit code 1 (no more exit code 5 or 6 on `snapshot save/restore` commands).
+- Require Go 1.10+.
 
 ### Added(`etcd`)