[3.13] gh-139308: Skip test_special_chars_csh on NetBSD due to csh variable expansion issue (GH-139341) (#139560)

gh-139308: Skip test_special_chars_csh on NetBSD due to csh variable expansion issue (GH-139341)

Skip test_special_chars_csh on NetBSD due to csh variable expansion issue
(cherry picked from commit ae6e7f572c18d9183cb23e6e53c3324dd9bf0c64)

Co-authored-by: Furkan Onder <furkanonder@protonmail.com>
Co-authored-by: Filipe Laíns 🇵🇸 <lains@riseup.net>