chore(session) Fix UP031 format specifier issue

src/libtmux/session.py:707:26: UP031 Use format specifiers instead of percent format
    |
705 |         if target_window:
706 |             if isinstance(target_window, int):
707 |                 target = "%s:%d" % (self.window_name, target_window)
    |                          ^^^^^^^ UP031
708 |             else:
709 |                 target = f"{target_window}"
    |
    = help: Replace with format specifiers

Author: tony

src/libtmux/session.py

@@ -704,7 +704,7 @@ def kill_window(self, target_window: t.Optional[str] = None) -> None:
         """
         if target_window:
             if isinstance(target_window, int):
-                target = "%s:%d" % (self.window_name, target_window)
+                target = f"{self.window_name}:{target_window}"
             else:
                 target = f"{target_window}"