Put conditioned header under appropriate feature configuration

- Add #if QT_CONFIG(itemmodel) for qitemselectionmodel.h usage
in removed_api.cpp

Amends 6324075a2d

Change-Id: If979d954caa6992a1e38675e8309fb33fe6b1ea2
Reviewed-by: Tasuku Suzuki <tasuku.suzuki@signal-slot.co.jp>
Reviewed-by: Ivan Solovev <ivan.solovev@qt.io>

src/corelib/compat/removed_api.cpp

@@ -990,7 +990,9 @@ bool QFileInfo::operator==(const QFileInfo &fileinfo) const
     return comparesEqual(*this, fileinfo);
 }
 
+#if QT_CONFIG(itemmodel)
 #include "qitemselectionmodel.h" // inlined API
+#endif // itemmodel
 
 #include "qjsonarray.h"