[3.14] gh-133503: clarify `compileall -s/-p` docs (GH-134756) (#134997)

gh-133503: clarify `compileall -s/-p` docs (GH-134756)
(cherry picked from commit fe6f8a3619242b287a793a5b5d8645f402482c71)

Co-authored-by: Rihaan Meher <meherrihaan@gmail.com>
Co-authored-by: Bénédikt Tran <10796600+picnixz@users.noreply.github.com>