Docs replace reference to 'getInitialState' with 'state' instance property in "Thinking in React" (#8059)

docs/thinking-in-react.md

@@ -124,7 +124,7 @@ Let's run through this strategy for our application:
   * The common owner component is `FilterableProductTable`.
   * It conceptually makes sense for the filter text and checked value to live in `FilterableProductTable`
 
-Cool, so we've decided that our state lives in `FilterableProductTable`. First, add a `getInitialState()` method to `FilterableProductTable` that returns `{filterText: '', inStockOnly: false}` to reflect the initial state of your application. Then, pass `filterText` and `inStockOnly` to `ProductTable` and `SearchBar` as a prop. Finally, use these props to filter the rows in `ProductTable` and set the values of the form fields in `SearchBar`.
+Cool, so we've decided that our state lives in `FilterableProductTable`. First, add an instance property `this.state = {filterText: '', inStockOnly: false}` to `FilterableProductTable`'s `constructor` to reflect the initial state of your application. Then, pass `filterText` and `inStockOnly` to `ProductTable` and `SearchBar` as a prop. Finally, use these props to filter the rows in `ProductTable` and set the values of the form fields in `SearchBar`.
 
 You can start seeing how your application will behave: set `filterText` to `"ball"` and refresh your app. You'll see that the data table is updated correctly.