[3.10] bpo-44257: fix "assigment_expr" typo + regenerate the grammar, and remove unused imports (GH-29393) (GH-29395)

Co-authored-by: Wim Glenn <wglenn@jumptrading.com>.
(cherry picked from commit 762173c6709f5cf3b59cbbe47d4e6fafbfe7ec2a)

Co-authored-by: wim glenn <wim.glenn@gmail.com>