Remove unused Map alias for VariantOrderedMap in convert example

Pick-to: 6.5
Task-number: QTBUG-111228
Change-Id: Ic82f7961df5f7a5bb0cd6cc113e4019508e58f47
Reviewed-by: Ivan Solovev <ivan.solovev@qt.io>
(cherry picked from commit 08ac3ddde73ce4ad2c069a74d46e4c627b0a6756)

examples/corelib/serialization/convert/converter.h

@@ -21,8 +21,6 @@ public:
             append({it.key(), it.value()});
     }
 };
-using Map = VariantOrderedMap;
-Q_DECLARE_METATYPE(Map)
 
 class Converter
 {