Use freq='D' instead of freq='d' in pd.timedelta_range (#10004)

Author: spencerkclark

xarray/tests/test_coding_times.py

@@ -1849,7 +1849,7 @@ def test_encode_cf_timedelta_casting_overflow_error(use_dask, dtype) -> None:
 def test_decode_timedelta(
     decode_times, decode_timedelta, expected_dtype, warns
 ) -> None:
-    timedeltas = pd.timedelta_range(0, freq="d", periods=3)
+    timedeltas = pd.timedelta_range(0, freq="D", periods=3)
     var = Variable(["time"], timedeltas)
     encoded = conventions.encode_cf_variable(var)
     if warns: