[3.10] gh-95994: Clarify escaped newlines. (GH-96066) (#96360)

* gh-95994: clarify escaped newlines.

* Rephrase ambiguous sentence.

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

* Use `<newline>` in escape sequences table.

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

Co-authored-by: C.A.M. Gerlach <CAM.Gerlach@Gerlach.CAM&gt;.>
(cherry picked from commit c3d591fd)

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