message: minor fixes in MPI docs
diff: @@ -23,7 +23,7 @@ See [**the complete test**](../../examples/mpi/mpi.cpp) and [**the configuration
  int my_function_to_test(MPI_Comm comm) {
  int rank;
  - MPI_comm_rank(comm,&rank);
  + MPI_Comm_rank(comm,&rank);
  if (rank == 0) {
  return 10;
  }
  @@ -68,7 +68,7 @@ mpirun -np 2 unit_test_executable.exe
  ```c++
  #define DOCTEST_CONFIG_IMPLEMENT
  -#include "doctest/mpi/doctest.h"
  +#include "doctest/extensions/doctest_mpi.h"
  int main(int argc, char** argv) {
  MPI_Init(&argc, &argv);
  