remove requires dask

Author: kmuehlbauer

xarray/tests/test_backends.py

@@ -5335,8 +5335,8 @@ def test_raise_writing_to_nczarr(self, mode) -> None:
 
 
 @requires_netCDF4
-@requires_dask
 def test_pickle_open_mfdataset_dataset():
+    # requires dask only if `parallel=True`
     with open_example_mfdataset(["bears.nc"]) as ds:
         assert_identical(ds, pickle.loads(pickle.dumps(ds)))