bpo-40994: Ungroup items in collections.abc documentation for improved clarity (GH-21880) (#21926)

Use a less surprising document structure.

Automerge-Triggered-By: @csabella
(cherry picked from commit 2ce39631f679e14132a54dc90ce764259d26e166)

Co-authored-by: Sydney Pemberton <46042811+sydneypemberton1986@users.noreply.github.com>
1 file changed