gh-133046: Reformat the ``ast`` module docstring (GH-133050)

* Fix formatting in module docstring for `ast` https://github.com/python/cpython/issues/133046
* #133046 ast docstring: remove header, dedent, 80-char width.
* Keep existing wrapping

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Co-authored-by: Adam Turner <9087854+aa-turner@users.noreply.github.com>