test: move the Self import into the TYPE_CHECKING block

Author: ppentchev

src/libtmux/test.py

@@ -10,8 +10,6 @@
 import time
 import typing as t
 
-from typing_extensions import Self
-
 from .exc import WaitTimeout
 
 logger = logging.getLogger(__name__)
@@ -20,6 +18,8 @@
     import types
     from collections.abc import Callable, Generator
 
+    from typing_extensions import Self
+
     from libtmux.server import Server
     from libtmux.session import Session
     from libtmux.window import Window