[3.11] `ast` docs: Fix incorrect link on `keyword` (GH-108728) (#108738)

`ast` docs: Fix incorrect link on `keyword` (GH-108728)

In two places, Sphinx was erroneously adding links to the `keyword` module instead of the `ast.keyword` class
(cherry picked from commit c1e2f3b2f70b8a72ea7e1bf792addf62a94ae65d)

Co-authored-by: Alex Povel <git@alexpovel.de>