Ensure GitLab Workhorse works with Go version 1.25.3

Overview

Upstream Go released 1.25.3.

This issue was generated per the Go upgrade process.

Please schedule this work for completion by the date defined in the parent epic.

cc @gitlab-org/maintainers/gitlab-workhorse

Definition of done

• Ensure GitLab Workhorse compiles with Go 1.25.3