test: series explode test (#606)

Author: chelsea-lin

tests/system/small/test_series.py

@@ -3463,9 +3463,8 @@ def foo(x: int, y: int, df):
     ],
 )
 def test_series_explode(data):
-    data = [[1, 2, 3], [], numpy.nan, [3, 4]]
     s = bigframes.pandas.Series(data)
-    pd_s = pd.Series(data)
+    pd_s = s.to_pandas()
     pd.testing.assert_series_equal(
         s.explode().to_pandas(),
         pd_s.explode(),