polymake SPKG.txt: Remove outdated info regarding macOS headers #29582
Description
CC: @jhpalmieri @dimpase @jplab @sophiasage
Component: packages: experimental
Author: Matthias Koeppe
Branch/Commit: 8c65337
Reviewer: Dima Pasechnik
Issue created by migration from https://trac.sagemath.org/ticket/29582