[3.14] gh-57095: Add note about input splitting in `datetime.*.strptime` (GH-131049) (GH-144735)

(cherry picked from commit 2e3e76e5cde34786780f5b3723f495fdbdf37c84)

Co-authored-by: Stan Ulbrych <89152624+StanFromIreland@users.noreply.github.com>