Use Final for Constant Literals in the stdlib (#12332)

Co-authored-by: Alex Waygood <Alex.Waygood@Gmail.com>

stdlib/pty.pyi

@@ -1,17 +1,17 @@
 import sys
 from collections.abc import Callable, Iterable
-from typing import Literal
+from typing import Final
 from typing_extensions import TypeAlias
 
 if sys.platform != "win32":
     __all__ = ["openpty", "fork", "spawn"]
     _Reader: TypeAlias = Callable[[int], bytes]
 
-    STDIN_FILENO: Literal[0]
-    STDOUT_FILENO: Literal[1]
-    STDERR_FILENO: Literal[2]
+    STDIN_FILENO: Final = 0
+    STDOUT_FILENO: Final = 1
+    STDERR_FILENO: Final = 2
 
-    CHILD: Literal[0]
+    CHILD: Final = 0
     def openpty() -> tuple[int, int]: ...
     def master_open() -> tuple[int, str]: ...  # deprecated, use openpty()
     def slave_open(tty_name: str) -> int: ...  # deprecated, use openpty()