[3.13] gh-146121: Clarify security model of pkgutil.getdata; revert checks (GH-148197) (#148205)

gh-146121: Clarify security model of pkgutil.getdata; revert checks (GH-148197)

This reverts commit bcdf231946b1da8bdfbab4c05539bb0cc964a1c7,
and clarifies get_data's security model.

(cherry picked from commit cf59bf76470f3d75ad47d80ffb8ce76b64b5e943)

Co-authored-by: Petr Viktorin <encukou@gmail.com>
Co-authored-by: Stan Ulbrych <stan@python.org>