Replaced old refs with new callback refs (#8254)

docs/thinking-in-react.md

@@ -132,8 +132,8 @@ You can start seeing how your application will behave: set `filterText` to `"bal
 
 ## Step 5: Add Inverse Data Flow
 
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 So far, we've built an app that renders correctly as a function of props and state flowing down the hierarchy. Now it's time to support data flowing the other way: the form components deep in the hierarchy need to update the state in `FilterableProductTable`.