Update CHANGELOG.md for 12.3.4

[ci skip]

CHANGELOG.md

@@ -2,6 +2,14 @@
 documentation](doc/development/changelog.md) for instructions on adding your own
 entry.
 
+## 12.3.4
+
+### Fixed (2 changes)
+
+- Fix cannot merge icon showing in dropdown for users who can merge. !17306
+- Fix pipelines for merge requests in project exports. !17844
+
+
 ## 12.3.2
 
 ### Security (12 changes)

changelogs/unreleased/31386-fix-cannot-merge-icon-is-wrong.yml

----
-title: Fix cannot merge icon showing in dropdown for users who can merge
-merge_request: 17306
-author:
-type: fixed

changelogs/unreleased/sh-fix-project-export-for-pipelines-for-mrs-mark2.yml

----
-title: Fix pipelines for merge requests in project exports
-merge_request: 17844
-author:
-type: fixed