bpo-23750: Document os-system, subprocess. Patch by Martin Panter. (GH-26016)

* Document os-system, subprocess Patch

* Update Doc/library/os.rst

Co-authored-by: Ken Jin <28750310+Fidget-Spinner@users.noreply.github.com>

Co-authored-by: Ken Jin <28750310+Fidget-Spinner@users.noreply.github.com>
2 files changed