Merge branch '397073-epic-relations-add-child-issue-to-epic' into 'master'

Update permissions for adding a child issue to an epic

See merge request https://gitlab.com/gitlab-org/gitlab/-/merge_requests/136322



Merged-by: Jarka Košanová <jarka@gitlab.com>
Approved-by: Joseph Wambua <jjoshua@gitlab.com>
Approved-by: Aboobacker MK <akarakath@gitlab.com>
Approved-by: Jarka Košanová <jarka@gitlab.com>
Reviewed-by: Aboobacker MK <akarakath@gitlab.com>
Co-authored-by: Eugenia Grieff <egrieff@gitlab.com>