fix: using Optional syntax

locust/stats.py

@@ -15,7 +15,7 @@
 from html import escape
 from itertools import chain
 from types import FrameType
-from typing import TYPE_CHECKING, Any, Callable, NoReturn, Protocol, TypedDict, TypeVar, cast
+from typing import TYPE_CHECKING, Any, Callable, NoReturn, Optional, Protocol, TypedDict, TypeVar, cast
 
 import gevent
 
@@ -185,7 +185,7 @@ class RequestStats:
     Class that holds the request statistics. Accessible in a User from self.environment.stats
     """
 
-    def __init__(self, use_response_times_cache=True, environment: Environment | None = None):
+    def __init__(self, use_response_times_cache=True, environment: Optional[Environment]=None):
         """
         :param use_response_times_cache: The value of use_response_times_cache will be set for each StatsEntry()
                                          when they are created. Settings it to False saves some memory and CPU