Docs: fix duplicate sections (CI docs) - Backport to CE
What does this MR do?
Backports https://gitlab.com/gitlab-org/gitlab-ee/merge_requests/4090 to CE
Related to https://gitlab.com/gitlab-org/gitlab-ce/issues/41138 and https://gitlab.com/gitlab-org/gitlab-ce/issues/41872
Edited by Marcia Ramos