Merge branch 'msj-epics-work-tems-doc' into 'master'

Style tweaks and tier info to epics work items doc

See merge request https://gitlab.com/gitlab-org/gitlab/-/merge_requests/158469



Merged-by: Lysanne Pinto <lpinto@gitlab.com>
Approved-by: Kushal Pandya <kushal@gitlab.com>
Approved-by: Lysanne Pinto <lpinto@gitlab.com>
Co-authored-by: Marcin Sedlak-Jakubowski <msedlakjakubowski@gitlab.com>