interpolate dates with xarray 2025.1.2

[crusaderky]

These fail after ugprading from xarray 2025.1.1 to 2025.1.2:

FAILED xarray_extras/tests/test_interpolate.py::test_dates[<M8[D]-<M8[D]] - AssertionError: Left and right DataArray objects are not close
Differing values:
L    array([13.005464, 20.      ])
R    array([10., 10.])
FAILED xarray_extras/tests/test_interpolate.py::test_dates[<M8[D]-<M8[s]] - AssertionError: Left and right DataArray objects are not close
Differing values:
L    array([13.005464, 20.      ])
R    array([10., 10.])
FAILED xarray_extras/tests/test_interpolate.py::test_dates[<M8[s]-<M8[D]] - AssertionError: Left and right DataArray objects are not close
Differing values:
L    array([13.005464, 20.      ])
R    array([10., 10.])
FAILED xarray_extras/tests/test_interpolate.py::test_dates[<M8[s]-<M8[s]] - AssertionError: Left and right DataArray objects are not close
Differing values:
L    array([13.005464, 20.      ])
R    array([10., 10.])
FAILED xarray_extras/tests/test_interpolate.py::test_dates[<M8[ns]-<M8[D]] - AssertionError: Left and right DataArray objects are not close
Differing values:
L    array([13.005464, 20.      ])
R    array([10., 10.])
FAILED xarray_extras/tests/test_interpolate.py::test_dates[<M8[ns]-<M8[s]] - AssertionError: Left and right DataArray objects are not close
Differing values:
L    array([13.005464, 20.      ])
R    array([10., 10.])