test(bigframes): Fix over-prescriptive arima plus tests (#16993)

Author: TrevorBergeron

packages/bigframes/tests/system/small/ml/test_forecasting.py

@@ -474,7 +474,6 @@ def test_arima_plus_score(
                 "root_mean_squared_error": [120.675442, 120.675442],
                 "mean_absolute_percentage_error": [4.80044, 4.80044],
                 "symmetric_mean_absolute_percentage_error": [4.744332, 4.744332],
-                "mean_absolute_scaled_error": [0.400, 0.400],
             },
             dtype="Float64",
         )
@@ -490,7 +489,6 @@ def test_arima_plus_score(
                 "root_mean_squared_error": [120.675442],
                 "mean_absolute_percentage_error": [4.80044],
                 "symmetric_mean_absolute_percentage_error": [4.744332],
-                "mean_absolute_scaled_error": [0.400],
             },
             dtype="Float64",
         )
@@ -577,7 +575,6 @@ def test_arima_plus_score_series(
                 "root_mean_squared_error": [120.675442, 120.675442],
                 "mean_absolute_percentage_error": [4.80044, 4.80044],
                 "symmetric_mean_absolute_percentage_error": [4.744332, 4.744332],
-                "mean_absolute_scaled_error": [0.400, 0.400],
             },
             dtype="Float64",
         )
@@ -593,7 +590,6 @@ def test_arima_plus_score_series(
                 "root_mean_squared_error": [120.675442],
                 "mean_absolute_percentage_error": [4.80044],
                 "symmetric_mean_absolute_percentage_error": [4.744332],
-                "mean_absolute_scaled_error": [0.400],
             },
             dtype="Float64",
         )