Adopt the same code that KInfoCenter uses for this tooltip and hardcode a 24px icon size
for tooltip child items instead of using the `KIconLoader::MainToolbar` size (which is
not really semantically correct anyway, since this is not a main toolbar).
By hardcoding 24x24, we ensure that KIconLoader downscales the nice 32x32 color versions of the icons rather than using the 22x22 versions of some of these icons, which we don't want.
BUG: 386748
FIXED-IN: 5.12.8