Some cosmetics on the 3.8 changelogs (#8214)

* Some cosmetics on the 3.8 changelogs

* More cosmetics on the 3.8 changelogs

Co-authored-by: Artem Pelenitsyn <a.pelenitsyn@gmail.com>

Co-authored-by: Artem Pelenitsyn <a.pelenitsyn@gmail.com>
Co-authored-by: mergify[bot] <37929162+mergify[bot]@users.noreply.github.com>
(cherry picked from commit a715d047)