Adapt Python bindings to renamed communicator
Communicator was renamed to MpiCommunicator in https://git.rz.tu-bs.de/irmb/VirtualFluids_dev/-/merge_requests/233
Communicator was renamed to MpiCommunicator in https://git.rz.tu-bs.de/irmb/VirtualFluids_dev/-/merge_requests/233