Update changelog for 16.3.4

[ci skip]

CHANGELOG.md

@@ -2,6 +2,17 @@
 documentation](doc/development/changelog.md) for instructions on adding your own
 entry.
+## 16.3.4 (2023-09-18)
+
+### Fixed (2 changes)
+
+- [Fix Geo secondary proxying Git pulls unnecessarily](gitlab-org/security/gitlab@d4ac7db42e80dec97fee07c50471f1e7b60d3bcc) **GitLab Enterprise Edition**
+- [Use new indexer, fix removing blobs from index](gitlab-org/security/gitlab@5d48e6871bc6f1c36b93c10f2a54cf28d6adbc65) **GitLab Enterprise Edition**
+
+### Security (1 change)
+
+- [Enforce that the policy is executed by the bot user](gitlab-org/security/gitlab@3f278f761f18ee0b14aca68e2e5f764e1e274176) ([merge request](gitlab-org/security/gitlab!3568))
+
 ## 16.3.3 (2023-09-12)
 ### Fixed (2 changes)