Update CHANGELOG for 8.43.0

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CHANGELOG

 # Changelog for gitlab-workhorse
 
+## v8.43.0
+
+### Changed
+- Remove ProcessReferences flag
+  https://gitlab.com/gitlab-org/gitlab-workhorse/-/merge_requests/543
+
+### Fixed
+- Fix nil pointer exception when no object storage config is defined
+  https://gitlab.com/gitlab-org/gitlab-workhorse/-/merge_requests/565
+
 ## v8.42.0
 
 ### Added

changelogs/unreleased/pb-remove-process-lsif-references-flag.yml

----
-title: Remove ProcessReferences flag
-merge_request: 543
-author:
-type: changed

changelogs/unreleased/sh-fix-nil-object-storage-creds.yml

----
-title: Fix nil pointer exception when no object storage config is defined
-merge_request: 565
-author:
-type: fixed