chore: remove redundant Python version checks

Now that Python 3.9 support has been dropped, inline code that was
gated behind sys.version_info checks for 3.9 and 3.10.

Author: Zac-HD

tenacity/__init__.py

@@ -89,14 +89,14 @@
 if t.TYPE_CHECKING:
     import types
 
-    from typing_extensions import ParamSpec, Self
+    from typing_extensions import Self
 
     from . import asyncio as tasyncio
     from .retry import RetryBaseT
     from .stop import StopBaseT
     from .wait import WaitBaseT
 
-    P = ParamSpec("P")
+    P = t.ParamSpec("P")
     R = t.TypeVar("R")