Unpin testslide from Python 3.10

Summary:
Python 3.10 [is deprecated and is going away](https://fb.workplace.com/groups/pythonfoundation/permalink/4266597163653730/).
Preemptive SEV: S615457

If this unpinning breaks your project, you **must** fix forward using Python 3.12+

If a forward fix is not immediately available, **and** this causes critical production issues, reach out via S615457.

Forced-unpinning diffs will be landed during the week of Feb 2, 2026.

Reviewed By: itamaro

Differential Revision: D91986248

fbshipit-source-id: 7ef5d01717d945ae14cda86de148224a39001a9f

Author: drinkmorewaterr

testslide/core/lib.py

@@ -14,7 +14,7 @@
 from functools import wraps
 from inspect import Traceback
 from types import FrameType
-from typing import Any, TYPE_CHECKING, Union
+from typing import Any, Self, TYPE_CHECKING, Union
 from unittest.mock import Mock
 
 import typeguard
@@ -371,7 +371,7 @@ def _validate_return_type(
                 expected_type = type_args[2]
 
         try:
-            if expected_type == typing_extensions.Self:
+            if expected_type == Self:
                 expected_type = template
             _validate_argument_type(expected_type, "return", value)
         except TypeCheckError as runtime_type_error: