[3.13] Fix a "doctest" block in `Doc/library/turtle.rst` (GH-128831) (#128835)

Fix a "doctest" block in `Doc/library/turtle.rst` (GH-128831)
(cherry picked from commit 1598e18a659ef3a533caa0a79a489a3ed1d80bdd)

Co-authored-by: Rafael Fontenelle <rffontenelle@users.noreply.github.com>