CoW: Remove remaining cow occurrences from tests
This should be all of them
For the skipped fastparquet tests, was going to open an issue on their side, but commented on an open one (they already saw the same failures on their CI in the meantime, https://github.com/dask/fastparquet/issues/919) Tbh I don’t really care. Not objecting to you investing time, but won’t bother with this

we deprecated this in dask/dask already and I would support a similar thing jere 