Drop joblib shim module in distributed (#3040)
Drop joblib shim module in distributed (#3040)

This already just raises an `ImportError` and has done so for a while.
Seems reasonable to just drop the module and let Python raise the
`ImportError` that it would anyways. Likely everyone has migrated to
this convention by now.
dask/distributed,dask/distributed,blaze/distributed,dask/distributed,blaze/distributed,dask/distributed