[3.11] gh-103820: IDLE: Do not interpret buttons 4/5 as scrolling on non-X11 (GH-103821) (GH-114902)

Also fix test_mousewheel: do not skip a check which was broken due to incorrect
delta on Aqua and XQuartz, and probably not because of `.update_idletasks()`.
(cherry picked from commit d25d4ee60cc789a8b9c222859bb720ade1ab2e30)

Co-authored-by: Christopher Chavez <chrischavez@gmx.us>