Backports test changes for fftfreq with chunks
Backports test changes for fftfreq with chunks

Backports some changes we submitted to Dask to test that `fftfreq` would
return the expected chunking in the resultant array.

ref: https://github.com/dask/dask/commit/fb72d81dad03a4b813bfefc81095df6926b61ffe

dask-image/dask-ndfourier