Fix unit tests for submonthly time series data

Author: tomvothecoder

tests/e3sm_diags/driver/utils/test_dataset_xr.py

@@ -1219,6 +1219,7 @@ def test_returns_time_series_dataset_using_sub_monthly_sets(self):
 
             result = ds.get_time_series_dataset("ts")
             expected = self.ds_ts.copy()
+            expected = expected.isel(time=slice(0, 3))
 
             xr.testing.assert_identical(result, expected)
 
@@ -1326,6 +1327,7 @@ def test_returns_time_series_dataset_without_centered_time_if_single_point_data(
 
         result = ds.get_time_series_dataset("ts", single_point=True)
         expected = self.ds_ts.copy()
+        expected = expected.isel(time=slice(0, 3))
 
         xr.testing.assert_identical(result, expected)