[3.13] gh-132346: Docs: Clarify that reference counts aren't stable between versions (GH-132352) (GH-136614)

gh-132346: Docs: Clarify that reference counts aren't stable between versions (GH-132352)
(cherry picked from commit 3dbe02ccd3eefc48ac9fa14427bb4cdb82d1ebae)

Co-authored-by: Peter Bierma <zintensitydev@gmail.com>