MNT: Avoid pandas warning

Apparently with Pandas 2.2.0 (tested in rc0) freq='H' is deprecated, in
favor of freq='h'. Since this works across our versions, go ahead and
change.

Author: dopplershift

tests/calc/test_basic.py

@@ -709,14 +709,14 @@ def test_smooth_window_1d_dataarray():
     temperature = xr.DataArray(
         [37., 32., 34., 29., 28., 24., 26., 24., 27., 30.],
         dims=('time',),
-        coords={'time': pd.date_range('2020-01-01', periods=10, freq='H')},
+        coords={'time': pd.date_range('2020-01-01', periods=10, freq='h')},
         attrs={'units': 'degF'})
     smoothed = smooth_window(temperature, window=np.ones(3) / 3, normalize_weights=False)
     truth = xr.DataArray(
         [37., 34.33333333, 31.66666667, 30.33333333, 27., 26., 24.66666667,
          25.66666667, 27., 30.] * units.degF,
         dims=('time',),
-        coords={'time': pd.date_range('2020-01-01', periods=10, freq='H')}
+        coords={'time': pd.date_range('2020-01-01', periods=10, freq='h')}
     )
     xr.testing.assert_allclose(smoothed, truth)