[3.12] Fix indentation in `json.AttrDict` REPL example (GH-104930) (#104931)

Fix indentation in `json.AttrDict` REPL example (GH-104930)

This is causing the docs to be rendered incorrectly.
(cherry picked from commit 38539ef1267f26a8b3508fcc8c6199cf46fc300b)

Co-authored-by: Alex Waygood <Alex.Waygood@Gmail.com>