Fix documentation for QML_ATTACHED and QML_FOREIGN

They can in fact not be combined.

Pick-to: 6.7 6.5 6.2
Change-Id: Ic01edf9328d7235511f305ed15114360b79d0a36
Reviewed-by: Fabian Kosmale <fabian.kosmale@qt.io>

src/qml/doc/src/qmlfunctions.qdoc

@@ -528,7 +528,7 @@
   \l QML_INTERFACE, \l QML_UNCREATABLE(), \l QML_SINGLETON,
   \l QML_ADDED_IN_VERSION(), \l QML_REMOVED_IN_VERSION(),
   \l QML_ADDED_IN_MINOR_VERSION(), \l QML_REMOVED_IN_MINOR_VERSION(),
-  \l QML_ATTACHED(), \l QML_EXTENDED(), or \l  QML_EXTENDED_NAMESPACE() macros
+  \l QML_EXTENDED(), or \l  QML_EXTENDED_NAMESPACE() macros
   in the enclosing C++ type do not apply to the enclosing type but instead to
   \a FOREIGN_TYPE. The enclosing type still needs to be registered with the
   \l {The Meta-Object System}{meta object system} using a \l Q_GADGET or
@@ -543,6 +543,9 @@
   not the foreign type. The \l {Foreign objects integration} chapter in
   \l {Writing advanced QML Extensions with C++} demonstrates this.
 
+  \note QML_ATTACHED() can currently not be redirected like this. It has to be
+  specificed in the same type that implements qmlAttachedProperties().
+
   \include {qualified-class-name.qdocinc} {class name must be qualified}
 
   \sa QML_ELEMENT, QML_NAMED_ELEMENT(), QML_FOREIGN_NAMESPACE()