Update CHANGELOG for 8.58.0

[ci skip]

CHANGELOG

 # Changelog for gitlab-workhorse
 
+## v8.58.0
+
+### Added
+- Support alternate document root directory
+  https://gitlab.com/gitlab-org/gitlab-workhorse/-/merge_requests/626
+
+### Fixed
+- Fix uploader not returning 413 when artifact too large
+  https://gitlab.com/gitlab-org/gitlab-workhorse/-/merge_requests/663
+- Auto-register Prometheus metrics
+  https://gitlab.com/gitlab-org/gitlab-workhorse/-/merge_requests/660
+
+### Other
+- Do not resize when image is less than 8 bytes
+  https://gitlab.com/gitlab-org/gitlab-workhorse/-/merge_requests/666
+
 ## v8.57.0
 
 ### Added

changelogs/unreleased/alipniagov-comment-on-buffer-size.yml

----
-title: Do not resize when image is less than 8 bytes
-merge_request: 666
-author:
-type: other

changelogs/unreleased/bjk-fix_metrics.yml

----
-title: Auto-register Prometheus metrics
-merge_request: 660
-author:
-type: fixed

changelogs/unreleased/sh-fix-gcs-entity-too-large.yml

----
-title: Fix uploader not returning 413 when artifact too large
-merge_request: 663
-author:
-type: fixed

changelogs/unreleased/sh-support-alt-document-root.yml

----
-title: Support alternate document root directory
-merge_request: 626
-author:
-type: added