Reinstore correct menu border color
cac4b544 introduced drawing separators of transparent QMenus with WindowText color with 0.25 opacity. While the change in drawMenuItemControl uses the correct condition, drawPanelMenuPrimitive checked whether the widget had an alpha channel. This is wrong because we set Qt::WA_TranslucentBackground always on all menus. The very low opacity made it look like the section headers, separators and highlight were drawing outside of the menu. BUG:428710