Use pallet property only when using qtquickcontrols 2.4
In qtquickcontrols 2.3, (released as part of qt 5.10). This properties
were not correctly registered
https://code.qt.io/cgit/qt/qtquickcontrols2.git/commit/?id=3c0f3ed5d5819a927d259e0dda7b3245cf43b110
So this breaks with qt 5.10, so we require qt 5.11 instead of qt 5.10 to
use this property