[doc] Fix gethostbyname_ex description (GH-28700) (GH-28742)

It seems part of `gethostbyname_ex` doc was copied from `gethostbyaddr`. The latter has an `ip_address` parameter whereas the former doesn't.
(cherry picked from commit 4103280b83e1419bef535a42813d6dbe83bfe880)

Co-authored-by: Andre Delfino <adelfino@gmail.com>