Align String str() with the format in FunctionSchema (#23201)
Summary:
old: string
new: str
Pull Request resolved: https://github.com/pytorch/pytorch/pull/23201
ghstack-source-id: 87125580
Reviewed By: zrphercule
Differential Revision: D16432340
fbshipit-source-id: 56bc7e8efbc2276315f464958cf38704f75dd06e
