[3.13] Docs: replace all `datetime` imports with `import datetime as dt` (GH-145640) (#146259)

Docs: replace all `datetime` imports with `import datetime as dt` (GH-145640)
(cherry picked from commit 83360b5869a4981c87dcb59d1186d26c41fe3386)

Co-authored-by: Hugo van Kemenade <1324225+hugovk@users.noreply.github.com>