Merge branch '464602-followup-epics-without-children-spacing' into 'master'

Remove extra gap when 0 roadmap epics have children

See merge request https://gitlab.com/gitlab-org/gitlab/-/merge_requests/156694



Merged-by: Florie Guibert <fguibert@gitlab.com>
Approved-by: Nick Leonard <nleonard@gitlab.com>
Approved-by: Rajan Mistry <rmistry@gitlab.com>
Approved-by: Florie Guibert <fguibert@gitlab.com>
Co-authored-by: Chad Lavimoniere <clavimoniere@gitlab.com>