Doc: drop obsolete snippet

QApplication::setColorSpec is obsolete. Drop the unused snippet
to avoid clutter when compiling snippet file (multiple main
entry points, etc.)

Change-Id: I5e34cc69aa6f1ccae248f625caa1528e70cb836e
Reviewed-by: Topi Reiniö <topi.reinio@qt.io>

src/gui/doc/snippets/code/src_gui_kernel_qapplication.cpp

@@ -77,16 +77,6 @@ QApplication::setStyle(QStyleFactory::create("fusion"));
 //! [1]
 
 
-//! [2]
-int main(int argc, char *argv[])
-{
-    QApplication::setColorSpec(QApplication::ManyColor);
-    QApplication app(argc, argv);
-    ...
-    return app.exec();
-}
-//! [2]
-
 
 //! [3]
 QSize MyWidget::sizeHint() const