setState update arrow function syntax

[hozefaj]

updating the docs to remove return while using arrow functions. Also helps to keep the snippets examples in sync with other docs https://github.com/facebook/react/blob/master/docs/docs/state-and-lifecycle.md#state-updates-may-be-asynchronous

[gaearon]

I want this section to be very explicit, so I'd rather not do it. In fact let's change it to use function here instead so that people can read it even if they're not proficient in ES6 yet. The other docs mention the function form.

[gaearon]

Please see the comment above

[hozefaj]

Sure will make the change. But I have noticed that across the docs, there is a mix of both arrow & function form.

Personally it makes sense to use arrow function, as I think as decent JS developer should not that syntax.

[bvaughn]

Thank you for filing this PR!

I'm sorry to be the bearer of bad news, but the documentation and source code for reactjs.org now lives in a different repository: reactjs/reactjs.org. (For more info on why we made this move, see issue #11075.)

Would you be willing to re-open this PR on the new repo? I promise we'll review it quickly!

[hozefaj]

New docs account for arrow functions correctly. This is no longer an issue on the new docs.