Suppress uneccessary xgcm DeprecationWarning for Axis which we don't use

Author: lpilz

tests/test_postprocess.py

@@ -79,7 +79,8 @@ def test_include_projection_coordinates_with_xgcm(sample_dataset):
     from xgcm import Grid
 
     dataset = xwrf.postprocess._include_projection_coordinates(sample_dataset)
-    grid = Grid(dataset)
+    with pytest.warns(DeprecationWarning):
+        grid = Grid(dataset, periodic=False)
 
     assert grid.axes['Y'].coords['center'] == 'south_north'
     assert grid.axes['Y'].coords['outer'] == 'south_north_stag'