QGestureManager: port Q_FOREACH to ranged-for [1/6]

The loop doesn't modify the QHash while iterating over it, so use
std::as_const.

Drive by change: Use asKeyValueRange() to get a key/value pair:
- No need to allocate a QStringList to hold the keys
- Prevent double lookup which happened when hash.value(key) was used
  inside the loop body

Task-number: QTBUG-115803
Change-Id: Ic0473c0971089f6ca75d3397209fe1c909e975a1
Reviewed-by: Christian Ehrlicher <ch.ehrlicher@gmx.de>

src/widgets/kernel/qgesturemanager.cpp

@@ -100,8 +100,7 @@ void QGestureManager::unregisterGestureRecognizer(Qt::GestureType type)
 {
     QList<QGestureRecognizer *> list = m_recognizers.values(type);
     m_recognizers.remove(type);
-    foreach (QGesture *g, m_gestureToRecognizer.keys()) {
-        QGestureRecognizer *recognizer = m_gestureToRecognizer.value(g);
+    for (const auto &[g, recognizer] : std::as_const(m_gestureToRecognizer).asKeyValueRange()) {
         if (list.contains(recognizer)) {
             m_deletedRecognizers.insert(g, recognizer);
         }