Replace SidebarHeightManager by CSS rules
This is the same as https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/13736/.
What does this MR do?
Remove SidebarHeightManager
and use CSS rules instead.
Why was this MR needed?
Too many factors influenced the sidebar height leading to several regressions.
Screenshots
What are the relevant issue numbers?
fixes https://gitlab.com/gitlab-org/gitlab-ce/issues/36447, fixes https://gitlab.com/gitlab-org/gitlab-ce/issues/36635, fixes https://gitlab.com/gitlab-org/gitlab-ce/issues/36855