stopping use function crossflowAllowed()

it turns on the crossflow when all the drawdown in the wrong direction,
then the well get rates in the wrong direction.

flow is not ready to handle this type of situation, then the only result
will be chopped time step.

opm/autodiff/WellInterface.hpp

@@ -429,8 +429,6 @@ namespace Opm
 
 }
 
-}
-
 #include "WellInterface_impl.hpp"
 
 #endif // OPM_WELLINTERFACE_HEADER_INCLUDED