ENH: Minor update to tutorial case schemes

tutorials/lagrangian/porousExplicitSourceReactingParcelFoam/verticalChannel/system/fvSolution

 /*--------------------------------*- C++ -*----------------------------------*\
 | =========                 |                                                 |
 | \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox           |
-|  \\    /   O peration     | Version:  dev                                   |
+|  \\    /   O peration     | Version:  2.1.x                                 |
 |   \\  /    A nd           | Web:      www.OpenFOAM.org                      |
 |    \\/     M anipulation  |                                                 |
 \*---------------------------------------------------------------------------*/
@@ -52,7 +52,7 @@ solvers
         solver          GAMG;
         tolerance       0;
         relTol          0.1;
-        smoother        GaussSeidel;
+        smoother        DICGaussSeidel;
         nPreSweeps      0;
         nPostSweeps     2;
         cacheAgglomeration true;