Use std::exchange in Qt::endPropertyUpdateGroup()

Easier to read, saying in one line that for which the old code needed
three.

Task-number: QTBUG-110710
Change-Id: Ie2a1d11aefe0bdf5f4db0694832fce669de564fc
Reviewed-by: Fabian Kosmale <fabian.kosmale@qt.io>

src/corelib/kernel/qproperty.cpp

@@ -233,9 +233,7 @@ void Qt::endPropertyUpdateGroup()
     while (data) {
         for (qsizetype i = 0; i < data->used; ++i)
             data->notify(i);
-        auto *next = data->next;
-        delete data;
-        data = next;
+        delete std::exchange(data, data->next);
     }
 }