fix: ruff format expected string in test_execution_plan

Author: kosiew

python/tests/test_dataframe.py

@@ -731,7 +731,9 @@ def test_optimized_logical_plan(aggregate_df):
 def test_execution_plan(aggregate_df):
     plan = aggregate_df.execution_plan()
 
-    expected = "AggregateExec: mode=FinalPartitioned, gby=[c1@0 as c1], aggr=[sum(test.c2)]\n"  # noqa: E501
+    expected = (
+        "AggregateExec: mode=FinalPartitioned, gby=[c1@0 as c1], aggr=[sum(test.c2)]\n"  # noqa: E501
+    )
 
     assert expected == plan.display()