Merge branch '428853-fix-discussions-with-system-notes' into 'master'

Fix fetching discussions for group level work items with system notes

See merge request https://gitlab.com/gitlab-org/gitlab/-/merge_requests/135300



Merged-by: Felipe Artur <fcardozo@gitlab.com>
Approved-by: Felipe Artur <fcardozo@gitlab.com>
Reviewed-by: Eulyeon Ko <5961404-euko@users.noreply.gitlab.com>
Co-authored-by: Mario Celi <mcelicalderon@gitlab.com>