Minor documentation issue at JSX section (render functions)

[jbruni]

It says it might feel painful that we're using 14 lines above ... but the only example above with 14 lines is far far away in the beginning of the document - and it is not interchangeable by the JSX example which follows:

https://github.com/vuejs/vuejs.org/blob/master/src/guide/render-function.md#jsx