[cleanup] correct input file for exercise-biomin

exercises/solution/exercise-biomineralization/CMakeLists.txt

 # executables for exercisebiomin
 dune_add_test(NAME exercisebiomin_solution
               SOURCES exercisebiomin.cc
-              CMD_ARGS exercisebiomin.input)
+              CMD_ARGS exercisebiomin_solution.input)
 
 # add tutorial to the common target
 add_dependencies(test_exercises exercisebiomin_solution)