fix docs link for useSyncExternalStore (#26452)

## Summary

Update readme to new documentation links to
[`React.useSyncExternalStore`](https://react.dev/reference/react/useSyncExternalStore

## How did you test this change?

This is just a documentation change, so we don't need to test it

Co-authored-by: 田源 <tianyuan@eol.cn>