Failing `save_intermediate_data` method MPI tests

[yousefmoazzam]

When running the MPI tests locally, I see two failing tests:

FAILED tests/test_methods.py::test_save_intermediate_data_chunked_compressed[1000] - AssertionError: assert (10, 10, 10) == (1, 10, 10)
FAILED tests/test_methods.py::test_save_intermediate_data_frames_per_chunk_mpi[1000] - AssertionError: assert (10, 10, 10) == (1, 10, 10)
============================================================================= 2 failed, 127 passed, 1 skipped, 624 deselected in 2.00s ============================================================================

[yousefmoazzam]

Possibly was caused by #661, I can't remember if I ran the MPI tests when developing that change.

If so, the tests may simply need changing to the new expected values (due to the setting of frames per chunk to 1 not being the intended behaviour anymore).