Doc: align the explanation with real code

Fixes: QTBUG-65661
Change-Id: I3f82bd3428c4a19f80864c376bda5d23b92c2896
Reviewed-by: Venugopal Shivashankar <Venugopal.Shivashankar@qt.io>

examples/activeqt/hierarchy/doc/src/hierarchy.qdoc

@@ -56,7 +56,7 @@
     name. The widget is also shown explicitly.
 
     \snippet activeqt/hierarchy/objects.cpp 2
-    The \c subWidget slot uses the \c QObject::child() function and
+    The \c subWidget slot uses the \c QObject::findChild() function and
     returns the first child of type \c QSubWidget that has the requested
     name.