[Cleanup] Do not use addProduct() needlessly

dune/tectonic/myblockproblem.hh

@@ -149,7 +149,7 @@ template <class MyConvexProblemTypeTEMPLATE> class MyBlockProblem {
     for (size_t i = 0; i < problem.A.N(); ++i) {
       auto const end = problem.A[i].end();
       for (auto it = problem.A[i].begin(); it != end; ++it)
-        Arithmetic::addProduct(linearization.A[i][it.index()], 1.0, *it);
+        linearization.A[i][it.index()] += *it;
     }
 
     // compute nonlinearity part of hessian