Update os.fspath(path: PathLike) to return Any since Union return types are troublesome

Author: sproshev

stdlib/3/os/__init__.pyi

@@ -198,7 +198,7 @@ if sys.version_info >= (3, 6):
     @overload
     def fspath(path: bytes) -> bytes: ...
     @overload
-    def fspath(path: PathLike) -> Union[str, bytes]: ...
+    def fspath(path: PathLike) -> Any: ...
 
 def get_exec_path(env: Optional[Mapping[str, str]] = ...) -> List[str]: ...
 # NOTE: get_exec_path(): returns List[bytes] when env not None