Update CHANGELOG for 8.48.0

[ci skip]

CHANGELOG

 # Changelog for gitlab-workhorse
 
+## v8.48.0
+
+### Changed
+- Switch image scaler to a Go-only solution
+  https://gitlab.com/gitlab-org/gitlab-workhorse/-/merge_requests/603
+
+### Other
+- Push uploader control flow into objectstore package
+  https://gitlab.com/gitlab-org/gitlab-workhorse/-/merge_requests/608
+
 ## v8.47.0
 
 ### Added

changelogs/unreleased/jv-uploader-readerfrom.yml

----
-title: Push uploader control flow into objectstore package
-merge_request: 608
-author:
-type: other

changelogs/unreleased/mk-golang-only-image-scaler.yml

----
-title: Switch image scaler to a Go-only solution
-merge_request: 603
-author:
-type: changed