[3.11] gh-94300: Update datetime.strptime documentation (GH-95318) (#103785)

gh-94300: Update datetime.strptime documentation (GH-95318)

The new wording better reflects the cases where `datetime.strptime` differs from` time.strptime`.

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(cherry picked from commit 5b404d6cad2bf53295fdf96305f95efe1ea0174e)

Co-authored-by: Howie Zhao <howiezhaohr@hotmail.com>
Co-authored-by: Paul Ganssle <git@m.ganssle.io>
Co-authored-by: Łukasz Langa <lukasz@langa.pl>
Co-authored-by: Alexander Belopolsky <abalkin@users.noreply.github.com>