[3.12] shlex docs: remove outdated note (GH-106463) (#106466)

shlex docs: remove outdated note (GH-106463)

As the versionchanged notice says, this note is no longer true on 3.12+.
(cherry picked from commit c16ea94abc73c0098b484f7e2ec23bfd9c36b67c)

Co-authored-by: Jelle Zijlstra <jelle.zijlstra@gmail.com>