Inappropriate use of QSKIP in QTabBar autotest

In qtbase/tests/auto/widgets/widgets/qtabbar/tst_qtabbar.cpp, the sizeHints() test function is effectively disabled with:

QSKIP("To be fixed on Mac (font size below not large enough) and Linux QWS (probably too large for the screen).");

If this skip was added due to a known bug, it would be better to use QEXPECT_FAIL() here, so that when the bug is fixed the test clearly reports that it needs to be updated. (If this remains a QSKIP, there is no warning that the test is out-of-date and the bug could reappear without anybody being informed.) The QEXPECT_FAIL should refer to an appropriate bug report documenting the known bug.

If the skip was added to avoid a piece of code that crashes, the text of the skip message must be updated to refer to an appropriate bug report.