[convmix] adapt CMakeLists and references to new TEnd

lecture/mm/convectivemixing/CMakeLists.txt

@@ -5,8 +5,8 @@ dune_add_test(NAME convmixexercise
               COMMAND ${dumux_INCLUDE_DIRS}/bin/testing/runtest.py
               CMD_ARGS  --script fuzzy
                         --files ${CMAKE_SOURCE_DIR}/lecture/references/convmix-reference.vtu
-                                 ${CMAKE_CURRENT_BINARY_DIR}/convmix-00019.vtu
-                        --command "${CMAKE_CURRENT_BINARY_DIR}/convmixexercise")
+                                 ${CMAKE_CURRENT_BINARY_DIR}/convmix-00021.vtu
+                        --command "${CMAKE_CURRENT_BINARY_DIR}/convmixexercise -TimeLoop.TEnd 1.9e8")
 
 
 # headers for installation and headercheck