Improve performance of group work items query

See merge request https://gitlab.com/gitlab-org/gitlab/-/merge_requests/141973



Merged-by: Andy Soiron <asoiron@gitlab.com>
Approved-by: Doug Stull <dstull@gitlab.com>
Approved-by: Andy Soiron <asoiron@gitlab.com>
Co-authored-by: Heinrich Lee Yu <heinrich@gitlab.com>