tst_QWidget::setToolTip fails on OS X 10.10

FAIL!  : tst_QWidget::setToolTip() Compared values are not the same
   Actual   (spy1.count()): 0
   Expected (1)           : 1
   Loc: [tst_qwidget.cpp(5715)]

tst_QWidget::setToolTip() fails quite frequently in the CI (script that collects all the fails from last week counts 48 and in the grafana dashboard 29 fails). That particular test has been blacklisted already from OS X 10.9.Also the test accounts for QTest::qWaitForWindowExposed() which is more problematic on macOS than on other platforms.

See discussions about it here:

https://bugreports.qt.io/browse/QTBUG-52594 "Make a platform-aware qWaitForWindowExposed()/Active()"
https://bugreports.qt.io/browse/QTBUG-53252 "isExposed() returns true also if window minimized or completely covered"
https://bugreports.qt.io/browse/QTBUG-26669 "Tooltip on Mac doesn't show up property (and othe focus issues?)"

I'm suggesting to blacklist also this one based on the fact that QTest::qWaitForWindowExposed() cannot be trusted especially on macOS.