Use Python 3.9 syntax in examples (#37279)

Signed-off-by: cyy <cyyever@outlook.com>

examples/legacy/benchmarking/plot_csv_file.py

@@ -15,7 +15,7 @@
 import csv
 from collections import defaultdict
 from dataclasses import dataclass, field
-from typing import List, Optional
+from typing import Optional
 
 import matplotlib.pyplot as plt
 import numpy as np
@@ -59,7 +59,7 @@ class PlotArguments:
         default=None,
         metadata={"help": "Filename under which the plot will be saved. If unused no plot is saved."},
     )
-    short_model_names: Optional[List[str]] = list_field(
+    short_model_names: Optional[list[str]] = list_field(
         default=None, metadata={"help": "List of model names that are used instead of the ones in the csv file."}
     )