CppEditor: Add missing namespace

Like the comment says. Amends 284817fae6.

Task-number: QTCREATORBUG-26304
Change-Id: I6cee9d84cedafa02dce14372e65672731e3e5cfc
Reviewed-by: Christian Stenger <christian.stenger@qt.io>

src/plugins/cppeditor/cppprojectupdater.h

@@ -47,7 +47,7 @@ public:
     CppProjectUpdaterFactory();
 
     // keep the namespace, for the type name in the invokeMethod call
-    Q_INVOKABLE CppProjectUpdaterInterface *create();
+    Q_INVOKABLE CppEditor::CppProjectUpdaterInterface *create();
 };
 
 } // namespace Internal