[3.12] gh-126165: Improve docs of function `math.isclose` (GH-126215) (#126381)

gh-126165: Improve docs of function `math.isclose` (GH-126215)
(cherry picked from commit 081706f873b7d1a10b27016a9ed350b20c719709)

Co-authored-by: Zhikang Yan <2951256653@qq.com>
Co-authored-by: Sergey B Kirpichev <skirpichev@gmail.com>
Co-authored-by: Carol Willing <carolcode@willingconsulting.com>
Co-authored-by: Terry Jan Reedy <tjreedy@udel.edu>