[cleanup] Remove deprecated header arithmetic.hh

This has been deprecated and superseded by `Dune::MatrixVector::`
long time ago (about 8 years).

dune/solvers/common/CMakeLists.txt

 install(FILES
-    arithmetic.hh
     boxconstraint.hh
     canignore.hh
     copyorreference.hh

dune/solvers/common/arithmetic.hh

-// -*- tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 4 -*-
-// vi: set et ts=8 sw=4 sts=4:
-#ifndef ARITHMETIC_HH
-#define ARITHMETIC_HH
-
-#warning arithmetic.hh is deprecated, please use dune-matrix-vector instead!
-
-#include <dune/matrix-vector/axpy.hh>
-#include <dune/matrix-vector/axy.hh>
-#include <dune/matrix-vector/crossproduct.hh>
-#include <dune/matrix-vector/matrixtraits.hh>
-#include <dune/matrix-vector/promote.hh>
-#include <dune/matrix-vector/scalartraits.hh>
-#include <dune/matrix-vector/transpose.hh>
-
-namespace Arithmetic
-{
-    using Dune::MatrixVector::Promote;
-    using Dune::MatrixVector::ScalarTraits;
-    using Dune::MatrixVector::MatrixTraits;
-    using Dune::MatrixVector::Transposed;
-    using Dune::MatrixVector::addProduct;
-    using Dune::MatrixVector::subtractProduct;
-    using Dune::MatrixVector::crossProduct;
-    using Dune::MatrixVector::transpose;
-    using Dune::MatrixVector::Axy;
-    using Dune::MatrixVector::bmAxy;
-}
-
-#endif

dune/solvers/common/staticmatrixtools.hh

@@ -16,8 +16,6 @@
 #include <dune/matrix-vector/scalartraits.hh>
 #include <dune/matrix-vector/transformmatrix.hh>
 
-#include "arithmetic.hh"
-
 namespace StaticMatrix
 {
         // type promotion (smallest matrix that can hold the sum of two matrices *******************