Update deprecated Python 3.8 typing (#13971)

benchmarks/backend_request_func.py

@@ -6,7 +6,7 @@ import sys
 import time
 import traceback
 from dataclasses import dataclass, field
-from typing import List, Optional, Union
+from typing import Optional, Union
 
 import aiohttp
 import huggingface_hub.constants
@@ -41,8 +41,8 @@ class RequestFuncOutput:
     latency: float = 0.0
     output_tokens: int = 0
     ttft: float = 0.0  # Time to first token
-    itl: List[float] = field(
-        default_factory=list)  # List of inter-token latencies
+    itl: list[float] = field(
+        default_factory=list)  # list of inter-token latencies
     tpot: float = 0.0  # avg next-token latencies
     prompt_len: int = 0
     error: str = ""