refactor(factory): add compatibility with Python 3.9

- Import TypeGuard from typing_extensions for Python versions < 3.10
- Import TypeGuard from typing for Python versions >= 3.10
- This change ensures compatibility with Python 3.9 and newer versions

src/sqlalchemy_dlock/factory.py

@@ -1,4 +1,10 @@
-from typing import Type, TypeGuard, TypeVar, Union
+import sys
+from typing import Type, TypeVar, Union
+
+if sys.version_info < (3, 10):  # pragma: no cover
+    from typing_extensions import TypeGuard
+else:  # pragma: no cover
+    from typing import TypeGuard
 
 from sqlalchemy.engine import Connection
 from sqlalchemy.ext.asyncio import AsyncConnection, AsyncSession, async_scoped_session