QVariant: fix incorrect warning about duplicated alias where there isn't

We were always matching a type name to itself because we forgot to
advance the iterator after we did match. The issue was introduced in
commit 46dc8e453a.

Fixes: QTBUG-99620
Task-number: QTBUG-96916
Pick-to: 6.3 6.2
Change-Id: Ib42b3adc93bf4d43bd55fffd16c8a5df6306e404
Reviewed-by: Friedemann Kleint <Friedemann.Kleint@qt.io>
Reviewed-by: Marc Mutz <marc.mutz@qt.io>
Reviewed-by: Jonas Kvinge <jonas@jkvinge.net>

src/corelib/kernel/qmetatype.cpp

@@ -200,6 +200,7 @@ const char *QtMetaTypePrivate::typedefNameForType(const QtPrivate::QMetaTypeInte
         if (it.key() == officialName)
             continue;               // skip the official name
         name = it.key().constData();
+        ++it;
         break;
     }