remove unused variable

[[Imported from SVN: r7392]]

dune/solvers/test/common.hh

@@ -236,8 +236,6 @@ void assemblePQ1RHS(const GridView& gridView, Vector& r, const Function& f)
     const IndexSet& indexSet = gridView.indexSet();
     FiniteElementCache cache;
 
-    int size = indexSet.size(dim);
-
     ElementIterator it = gridView.template begin<0>();
     ElementIterator end = gridView.template end<0>();
     for (; it != end; ++it)