Revert the "What's new" feature

What does this MR do?

This MR is to revert the changes merged in https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/23186

What are the relevant issue numbers?

Original issue: https://gitlab.com/gitlab-org/gitlab-ce/issues/25341 Issue with request to revert: https://gitlab.com/gitlab-org/gitlab-ce/issues/56828

Once this MR has been merged, I'll re-open the original issue and continue the discussion from the issue where the request to revert was raised.