Inappropriate use of QSKIP in QWidget autotest

In qtbase/tests/auto/widgets/kernel/qwidget/tst_qwidget.cpp, the raise() test function is partially disabled on Mac OS with:

#ifdef Q_OS_MAC
        QSKIP("Not yet sure why this fails.");
#endif

This is inappropriate for three reasons:

First, the QSKIP is inside a loop and will execute a return part of the way through the first iteration of the loop.

Second, the skip message instills absolutely no confidence in the quality of the test. The message should instead refer to an appropriate bug report so that someone will eventually get around to investigating the problem.

Third, it would be better to use QEXPECT_FAIL instead of QSKIP so that there will be a clear indication that the test needs updating should the problem be fixed.