bpo-45583: Correct datamodel documentation of int() (GH-29182) (GH-29285)

It should be noted that this part of the documentation is redundant with
function.rst's documentation of int. This one was correctly updated with Python 3.8.
(cherry picked from commit d9c1868c25ec6466e8d8ae21fe9315a8a03836ab)

Co-authored-by: Arthur Milchior <arthur@milchior.fr>