[test.operators.elliptic] update projection usage

dune/gdt/test/operators/elliptic.hh

@@ -557,7 +557,7 @@ struct EllipticMatrixOperatorTest : public EllipticProductBase<SpaceType>, publi
     auto op                      = make_elliptic_matrix_operator<MatrixType>(diffusion_factor, diffusion_tensor, space);
     // project the function
     DiscreteFunctionType discrete_function(space);
-    Operators::Projection<GridViewType>(space.grid_view()).apply(function, discrete_function);
+    project(space.grid_view(), function, discrete_function);
     // compute product
     const auto result = op->apply2(discrete_function, discrete_function);
     auto op_tbb = make_elliptic_matrix_operator<MatrixType>(diffusion_factor, diffusion_tensor, space);