chore(readme): remove Greenkeeper badge (#2)

Co-authored-by: greenkeeper[bot] <23040076+greenkeeper[bot]@users.noreply.github.com>

README.md

@@ -2,7 +2,7 @@
 
 [![npm version](https://img.shields.io/npm/v/@sweetalert2/eslint-config.svg)](https://www.npmjs.com/package/@sweetalert2/eslint-config)
 [![semantic-release](https://img.shields.io/badge/%20%20%F0%9F%93%A6%F0%9F%9A%80-semantic--release-e10079.svg)](https://github.com/sweetalert2/eslint-config/blob/master/CHANGELOG.md)
-[![Greenkeeper badge](https://badges.greenkeeper.io/sweetalert2/eslint-config.svg)](https://greenkeeper.io/)
+
 
 > ESLint [shareable config](http://eslint.org/docs/developer-guide/shareable-configs.html) for the [SweetAlert2](https://github.com/sweetalert2/sweetalert2) JS/TS coding style