Update CHANGELOG.md for 12.9.4

[ci skip]

CHANGELOG.md

@@ -2,6 +2,17 @@
 documentation](doc/development/changelog.md) for instructions on adding your own
 entry.
 
+## 12.9.4 (2020-04-16)
+
+### Fixed (5 changes, 1 of them is from the community)
+
+- Fix not working File upload from Project overview page. !26828 (Gilang Gumilar)
+- Fix storage rollback regression caused by previous refactor. !28496
+- Fix incorrect regex used in FileUploader#extract_dynamic_path. !28683
+- Fully qualify id columns for keyset pagination (Projects API). !29026
+- Fix Slack notifications when upgrading from old GitLab versions. !29111
+
+
 ## 12.9.3 (2020-04-14)
 
 ### Security (3 changes)

changelogs/unreleased/209059-fix-project-show-file-upload-not-working.yml

----
-title: Fix not working File upload from Project overview page.
-merge_request: 26828
-author: Gilang Gumilar
-type: fixed

changelogs/unreleased/209940-geo-fails-to-sync-file-uploads-with-improper-formatted-path.yml

----
-title: Fix incorrect regex used in FileUploader#extract_dynamic_path
-merge_request: 28683
-author:
-type: fixed

changelogs/unreleased/211452-rollback_to_legacy-causes-repos-to-404.yml

----
-title: Fix storage rollback regression caused by previous refactor
-merge_request: 28496
-author:
-type: fixed

changelogs/unreleased/212073-slack-notifications-stop-working-after-updating-gitlab.yml

----
-title: Fix Slack notifications when upgrading from old GitLab versions
-merge_request: 29111
-author:
-type: fixed

changelogs/unreleased/ab-keyset-ambig-bug.yml

----
-title: Fully qualify id columns for keyset pagination (Projects API)
-merge_request: 29026
-author:
-type: fixed