Add indexing of group wikis in index rake task

See merge request https://gitlab.com/gitlab-org/gitlab/-/merge_requests/127020



Merged-by: John Mason <9717668-johnmason@users.noreply.gitlab.com>
Approved-by: John Mason <9717668-johnmason@users.noreply.gitlab.com>
Reviewed-by: Terri Chu <tchu@gitlab.com>
Reviewed-by: Madelein van Niekerk <mvanniekerk@gitlab.com>
Co-authored-by: Terri Chu <tchu@gitlab.com>
Co-authored-by: rkumar555 <rkumar@gitlab.com>
Co-authored-by: Ashraf Khamis <akhamis@gitlab.com>