[3.12] gh-130160: use `.. program::` directive for documenting `idle` CLI (GH-130278) (#130495)

gh-130160: use `.. program::` directive for documenting `idle` CLI (GH-130278)

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(cherry picked from commit 0ff16115741aeaaaf7f963f68d5c575efb960277)

Co-authored-by: Kanishk Pachauri <itskanishkp.py@gmail.com>