[3.13] gh-106318: Improve str.removeprefix() and str.removesuffix() docs (GH-143580) (#143615)

gh-106318: Improve str.removeprefix() and str.removesuffix() docs (GH-143580)

Add doctest role and 'See also'.
(cherry picked from commit 6d6c7ed73786915d16f6ac3d8b6e6d67f404209f)

Co-authored-by: Adorilson Bezerra <adorilson@gmail.com>