Remove obsoleted QIcon code from colorpaletteclient

The recently refactored UI doesn't rely on icon theming anymore.

Amends: 7a62659880

Pick-to: 6.7
Change-Id: I59bc7df167cf6cbd6b26cbd494674927f81f319e
Reviewed-by: Matthias Rauter <matthias.rauter@qt.io>

examples/demos/colorpaletteclient/main.cpp

@@ -4,12 +4,10 @@
 #include <QtQml/qqmlapplicationengine.h>
 #include <QtQml/qqmlcontext.h>
 #include <QtGui/qguiapplication.h>
-#include <QtGui/qicon.h>
 
 int main(int argc, char *argv[])
 {
     QGuiApplication app(argc, argv);
-    QIcon::setThemeName("colorpaletteclient");
 
     QQmlApplicationEngine engine;
 #ifdef Q_OS_MACOS