[3.9] gh-95778: Mention sys.set_int_max_str_digits() in error message (#96874) (#96877)

When ValueError is raised if an integer is larger than the limit,
mention sys.set_int_max_str_digits() in the error message.

(cherry picked from commit e841ffc9)

Co-authored-by: Ned Deily <nad@python.org>