corrected minor inconsistency of decoupled tutorial with its docu (output...

corrected minor inconsistency of decoupled tutorial with its docu (output interval too small). reviewed by Philipp

git-svn-id: svn://svn.iws.uni-stuttgart.de/DUMUX/dumux/trunk@9072 2fb0f335-1f38-0410-981e-8018bf24f1b0