Remove deprecated header dunefunctionsmassassembler.hh

dune/fufem/assemblers/localassemblers/dunefunctionsmassassembler.hh

-#pragma once
-
-#warning This file is deprecated!  Please use Dune::Fufem::MassAssembler from the file massassembler.hh!
-
-#include <dune/fufem/assemblers/localassemblers/massassembler.hh>
-
-namespace Dune::Fufem
-{
-  using DuneFunctionsLocalMassAssembler = Dune::Fufem::MassAssembler;
-} // namespace Dune::Fufem