add missing release note in 6.5.7 (#16471) (#16491)

releases/release-6.5.7.md

@@ -64,6 +64,7 @@ Quick access: [Quick start](https://docs.pingcap.com/tidb/v6.5/quick-start-with-
     - Fix the issue that TiDB panics and reports an error `invalid memory address or nil pointer dereference` [#42739](https://github.com/pingcap/tidb/issues/42739) @[CbcWestwolf](https://github.com/CbcWestwolf)
     - Fix the issue that CTE queries might report an error `type assertion for CTEStorageMap failed` during the retry process [#46522](https://github.com/pingcap/tidb/issues/46522) @[tiancaiamao](https://github.com/tiancaiamao)
     - Fix the issue that Daylight Saving Time is displayed incorrectly in some time zones [#49586](https://github.com/pingcap/tidb/issues/49586) @[overvenus](https://github.com/overvenus)
+    - Fix the issue that the completion times of two DDL tasks with dependencies are incorrectly sequenced [#49498](https://github.com/pingcap/tidb/issues/49498) @[tangenta](https://github.com/tangenta)
 
 + TiKV