Remove unnecessary cast to uint64_t.

The cast to uint64_t breaks build when platform pointer is not 64 bits. The cast seems unnecessary, and likely inherited from the initial catalyst_replay code.

(...)/adioscatalyst/AdiosReplay/AdiosReplay.cxx:544:38: error: invalid conversion from ‘uint64_t’ {aka ‘
long unsigned int’} to ‘MPI_Comm’ {aka ‘ompi_communicator_t*’} [-fpermissive]
 544 |   adios2::ADIOS adiosReader(argv[1], communicator);
     |                                      ^~~~~~~~~~~~
     |                                      |
     |                                      uint64_t {aka long unsigned int}