Update CHANGELOG for release v3.8.3-patch.9 (#3536)

Co-authored-by: mo3et <34803812+mo3et@users.noreply.github.com>
Co-authored-by: chao <48119764+withchao@users.noreply.github.com>

CHANGELOG/CHANGELOG-3.8.md

@@ -1,3 +1,13 @@
+## [v3.8.3-patch.9](https://github.com/openimsdk/open-im-server/releases/tag/v3.8.3-patch.9) 	(2025-08-19)
+
+### New Features
+* feat: enable redis aof-use-rdb-preamble && disable auto rdb [Created [#3535](https://github.com/openimsdk/open-im-server/pull/3535)
+
+### Bug Fixes
+* fix: fill in the most recent sendTime for a gap message to prevent th… [#3523](https://github.com/openimsdk/open-im-server/pull/3523)
+
+**Full Changelog**: [v3.8.3-patch.8...v3.8.3-patch.9](https://github.com/openimsdk/open-im-server/compare/v3.8.3-patch.8...v3.8.3-patch.9)
+
 ## [v3.8.3-patch.8](https://github.com/openimsdk/open-im-server/releases/tag/v3.8.3-patch.8) 	(2025-08-13)
 
 ### Bug Fixes