Fix win32 spawning_popen return type

Author: donbarbos

stdlib/multiprocessing/context.pyi

@@ -207,7 +207,7 @@ if sys.platform != "win32":
     def set_spawning_popen(popen: popen_forkserver.Popen | popen_spawn_posix.Popen | None) -> None: ...
 
 else:
-    def get_spawning_popen() -> popen_forkserver.Popen | popen_spawn_win32.Popen | None: ...
-    def set_spawning_popen(popen: popen_forkserver.Popen | popen_spawn_win32.Popen | None) -> None: ...
+    def get_spawning_popen() -> popen_spawn_win32.Popen | None: ...
+    def set_spawning_popen(popen: popen_spawn_win32.Popen | None) -> None: ...
 
 def assert_spawning(obj: Any) -> None: ...