Remove mention of stage-2 in readme (#1325)

readme.md

@@ -688,7 +688,7 @@ test(t => {
 
 ### ES2017 support
 
-AVA comes with built-in support for ES2017 through [Babel 6](https://babeljs.io). Just write your tests in ES2017. No extra setup needed. You can use any Babel version in your project. We use our own bundled Babel with our [`@ava/stage-4`](https://github.com/avajs/babel-preset-stage-4) and [`stage-2`](https://babeljs.io/docs/plugins/preset-stage-2/) preset, as well as [custom transforms](https://github.com/avajs/babel-preset-transform-test-files) for test and helper files.
+AVA comes with built-in support for ES2017 through [Babel 6](https://babeljs.io). Just write your tests in ES2017. No extra setup needed. You can use any Babel version in your project. We use our own bundled Babel with our [`@ava/stage-4`](https://github.com/avajs/babel-preset-stage-4) preset, as well as [custom transforms](https://github.com/avajs/babel-preset-transform-test-files) for test and helper files.
 
 The corresponding Babel config for AVA's setup is as follows: