macOS: Remove reference to the Carbon framework

Change-Id: I4e9871287c8fd54c5f85ed7d7ccaa97d8ef5a51f
Reviewed-by: Morten Johan Sørvig <morten.sorvig@qt.io>

doc/src/platforms/macos.qdoc

@@ -763,7 +763,7 @@
     Usually, when referring to a native \macos application, \e native means an
     application that interfaces directly to the underlying window system, rather
     than one that uses some intermediary layer. Qt applications run as first
-    class citizens, just like Cocoa and Carbon applications. We use Cocoa
+    class citizens, just like Cocoa applications. We use Cocoa
     internally to communicate with the operating system.
 
 */