[stokes2c] update reference solution for the stokes 2c diffusion test

The fuzzycompare script seems to be not fuzzy enough. The differences
are due to the fact that the reference and the test solution have been /
are calculated on different systems. They are negligible.



git-svn-id: svn://svn.iws.uni-stuttgart.de/DUMUX/dumux/trunk@15075 2fb0f335-1f38-0410-981e-8018bf24f1b0