[3.13] gh-119802: Update memory management docs for free-threaded build (gh-124006) (#124054)

gh-119802: Update memory management docs for free-threaded build (gh-124006)

* gh-119802: Update memory management docs for free-threaded build

* nit

* nit

* Address code review

* nit

* Update Doc/c-api/memory.rst



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(cherry picked from commit e6bb1a2b28ac8aed1e1b7f1c74221ca1d02a7235)

Co-authored-by: Donghee Na <donghee.na@python.org>
Co-authored-by: Sam Gross <colesbury@gmail.com>