test: Re-enabling tst_QScrollBar::task_209492() on Mac

This test has been XPASS'ing since a long time now.

Change-Id: Ibfcd1b5078e0b8efed9ed0740a4238d24ef8ca33
Reviewed-by: Rohan McGovern <rohan.mcgovern@nokia.com>
Reviewed-by: Morten Johan Sørvig <morten.sorvig@nokia.com>
Reviewed-by: Bradley T. Hughes <bradley.hughes@nokia.com>

tests/auto/widgets/widgets/qscrollbar/tst_qscrollbar.cpp

@@ -136,9 +136,6 @@ void tst_QScrollBar::task_209492()
     QApplication::sendEvent(verticalScrollBar, &mouseReleaseEvent);
 
     // Check that the action was triggered once.
-#ifdef Q_OS_MAC
-    QEXPECT_FAIL("", "Fix does does not work on Mac due to paint architechure differences.", Abort);
-#endif
     QCOMPARE(scrollArea.scrollCount, 1);
     QCOMPARE(spy.count(), 1);
 }