[3.12] gh-116851: Remove "from ctypes import *" from a ctypes example (GH-116852) (GH-116905)

It is confusing, because libc is not imported from ctypes,
but defined in previous examples, which already contain the import.
(cherry picked from commit 744c0777952f1e535d1192ee15b286aa67b61533)

Co-authored-by: jnchen <caojingchen@live.com>