Don't use QIcon::Selected state for selected icon

This causes selected monochrome Breeze icons to turn white as this state is meant for when the icon is actually painted ontop of
e.g. a blue highlighted area in a menu
Since the advanced icon configuration (where you could choose a custom hint color and other effects) has been removed in Plasma 5.13
and more importantly the fact that Dolphin always tints the icon in the highlight color disregarding any custom icon effects settings
this is an acceptable change.

CHANGELOG: Fixed monochrome icons turning invisible when selected

BUG: 398014
FIXED-IN: 18.08.2

Differential Revision: https://phabricator.kde.org/D15255