iOS: Fix compilation warning

warning: unused variable 'iface' [-Wunused-variable]

Change-Id: I882b71e5ae4afac1f3eb8b59d378b1a0c6fcade1
Reviewed-by: Frederik Gladhorn <frederik.gladhorn@digia.com>

src/plugins/platforms/ios/quiaccessibilityelement.mm

@@ -65,8 +65,7 @@
 
     QMacAccessibilityElement *element = cache->elementForId(anId);
     if (!element) {
-        QAccessibleInterface *iface = QAccessible::accessibleInterface(anId);
-        Q_ASSERT(iface);
+        Q_ASSERT(QAccessible::accessibleInterface(anId));
         element = [[self alloc] initWithId:anId withAccessibilityContainer: view];
         cache->insertElement(anId, element);
     }