Update CHANGELOG-EE.md for 12.4.3-ee

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CHANGELOG-EE.md

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+## 12.4.3
+
+### Fixed (2 changes)
+
+- Fix admin welcome image not found. !19676
+- Revert ES support for public/internal project snippets. !19715
+
+
 ## 12.4.2
 ### Fixed (1 change)

ee/changelogs/unreleased/34558-revert-es-project-snippets.yml

----
-title: Revert ES support for public/internal project snippets
-merge_request: 19715
-author:
-type: fixed

ee/changelogs/unreleased/34768-fix-welcome-images-for-admin.yml

----
-title: Fix admin welcome image not found
-merge_request: 19676
-author:
-type: fixed