fix: broken link (#6115)

Author: yuta-ike

src/content/reference/react/useRef.md

@@ -228,7 +228,7 @@ function MyComponent() {
 
 If you *have to* read [or write](/reference/react/useState#storing-information-from-previous-renders) something during rendering, [use state](/reference/react/useState) instead.
 
-When you break these rules, your component might still work, but most of the newer features we're adding to React will rely on these expectations. Read more about [keeping your components pure.](/learn/keeping-components-pure#where-you-can-cause-side-effects)
+When you break these rules, your component might still work, but most of the newer features we're adding to React will rely on these expectations. Read more about [keeping your components pure.](/learn/keeping-components-pure#where-you-_can_-cause-side-effects)
 
 </Pitfall>