Files with old-style Optional[Foo] or Union[Foo, Bar] syntax

[Akuli]

#5872 didn't handle all files. List taken from #5872:

• stdlib/_ast.pyi
• stdlib/_thread.pyi
• stdlib/ast.pyi
• stdlib/asyncio/tasks.pyi
• stdlib/configparser.pyi
• stdlib/ctypes/__init__.pyi
• stdlib/email/_header_value_parser.pyi
• stdlib/os/__init__.pyi
• stdlib/pickle.pyi
• stdlib/types.pyi
• stdlib/zoneinfo/__init__.pyi
• stubs/Jinja2/jinja2/nodes.pyi
• stubs/click/click/core.pyi
• stubs/requests/requests/sessions.pyi
• stubs/six/six/__init__.pyi
• stubs/typed-ast/typed_ast/ast27.pyi
• stubs/typed-ast/typed_ast/ast3.pyi