v8.5.3: add release notes (#21399) (#21606)

Author: ti-chi-bot

TOC.md

@@ -1093,6 +1093,7 @@
   - [Release Support Policy](https://www.pingcap.com/tidb-release-support-policy/)
   - [TiDB Installation Packages](/binary-package.md)
   - v8.5
+    - [8.5.3](/releases/release-8.5.3.md)
     - [8.5.2](/releases/release-8.5.2.md)
     - [8.5.1](/releases/release-8.5.1.md)
     - [8.5.0](/releases/release-8.5.0.md)