Add comment to tst_QWidget::saveRestoreGeometry() for debugging

saveRestoreGeometry() somtimes creates a 29px offset when debugged in
Qt Creator, which makes the test fail.

This patch adds a code comment to make developers aware of this fact.

Pick-to: 6.2 6.4
Change-Id: I920bd02eb7543faf8b25a0a242b888f3a3745e2a
Reviewed-by: Richard Moe Gustavsen <richard.gustavsen@qt.io>

tests/auto/widgets/kernel/qwidget/tst_qwidget.cpp

@@ -4025,6 +4025,13 @@ void tst_QWidget::saveRestoreGeometry()
         QVERIFY(QTest::qWaitForWindowExposed(&widget));
         QApplication::processEvents();
 
+
+    /* ---------------------------------------------------------------------
+     * This test function is likely to flake when debugged with Qt Creator.
+     * (29px offset making the following QTRY_VERIFY2 fail)
+     * ---------------------------------------------------------------------
+     */
+
         QTRY_VERIFY2(HighDpi::fuzzyCompare(widget.pos(), position, m_fuzz),
                      qPrintable(HighDpi::msgPointMismatch(widget.pos(), position)));
         QCOMPARE(widget.size(), size);