CHANGELOG: update changelog 3.5

Add etcd_debugging_mvcc_current_revision and
etcd_debugging_mvcc_compact_revision.

CHANGELOG-3.5.md

@@ -53,6 +53,8 @@ Note that any `etcd_debugging_*` metrics are experimental and subject to change.
 - Deprecated `etcd_debugging_mvcc_delete_total` Prometheus metric. Use `etcd_mvcc_delete_total` instead.
 - Deprecated `etcd_debugging_mvcc_txn_total` Prometheus metric. Use `etcd_mvcc_txn_total` instead.
 - Deprecated `etcd_debugging_mvcc_range_total` Prometheus metric. Use `etcd_mvcc_range_total` instead.
+- Add [`etcd_debugging_mvcc_current_revision`](https://github.com/etcd-io/etcd/pull/11126) Prometheus metric.
+- Add [`etcd_debugging_mvcc_compact_revision`](https://github.com/etcd-io/etcd/pull/11126) Prometheus metric.
 
 ### etcd server