CI: nightly tests failing

[anissa111]

Nightly tests fail across all versions of python and OS since Saturday, December 3

• First failure here
• Most current failure at time of issue creation here
• Seem to be kicked off by the release of xarray 2022.12.0

Errors are all along the lines of:

======================================================================
ERROR: test_alt_coef (test.test_meteorology.Test_heat_index)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "/Users/anissaz/Desktop/GeoCAT/geocat-comp/test/test_meteorology.py", line 131, in test_alt_coef
    assert np.allclose(heat_index(self.t2, self.rh2, True),
  File "/Users/anissaz/Desktop/GeoCAT/geocat-comp/src/geocat/comp/meteorology.py", line 766, in heat_index
    heatindex = _heat_index(temperature, relative_humidity,
  File "/Users/anissaz/Desktop/GeoCAT/geocat-comp/src/geocat/comp/meteorology.py", line 111, in _heat_index
    heatindex = xr.where(temperature < 40, temperature, heatindex)
  File "/Users/anissaz/opt/miniconda3/envs/geocat_comp_build/lib/python3.10/site-packages/xarray/core/computation.py", line 1887, in where
    result.attrs = getattr(x, "attrs", {})
AttributeError: 'numpy.ndarray' object has no attribute 'attrs' 

Looking at the error coming from xarray, that section of the code was edited in this PR and included in the 2022.12.0 release three days ago