Update conditional-rendering.md (#990)

`componentWillUpdate` method will be called before the render method so the returning value of the render method does not affect.

content/docs/conditional-rendering.md

@@ -239,4 +239,4 @@ ReactDOM.render(
 
 [Try it on CodePen.](https://codepen.io/gaearon/pen/Xjoqwm?editors=0010)
 
-Returning `null` from a component's `render` method does not affect the firing of the component's lifecycle methods. For instance, `componentWillUpdate` and `componentDidUpdate` will still be called.
+Returning `null` from a component's `render` method does not affect the firing of the component's lifecycle methods. For instance `componentDidUpdate` will still be called.