gh-95913: Copyedit/improve Implementation Changes What's New section (GH-97720)

* Add and refine reST/Sphinx syntax for implementation changes section

* Clarify and refine wording in the Implementation Changes section

* Elide unnecessary comma

Co-authored-by: Ezio Melotti <ezio.melotti@gmail.com>

Co-authored-by: Ezio Melotti <ezio.melotti@gmail.com>
(cherry picked from commit 4e731814d781dae3419e981c0acc3ef833e26e8a)

Co-authored-by: C.A.M. Gerlach <CAM.Gerlach@Gerlach.CAM>