chore(readme): remove Greenkeeper badge

Author: greenkeeper[bot]

README.md

@@ -1,6 +1,6 @@
 # eslint-plugin-array-func
 
-[![Greenkeeper badge](https://badges.greenkeeper.io/freaktechnik/eslint-plugin-array-func.svg)](https://greenkeeper.io/) [![Build Status](https://travis-ci.com/freaktechnik/eslint-plugin-array-func.svg?branch=master)](https://travis-ci.com/freaktechnik/eslint-plugin-array-func) [![codecov](https://codecov.io/gh/freaktechnik/eslint-plugin-array-func/branch/master/graph/badge.svg)](https://codecov.io/gh/freaktechnik/eslint-plugin-array-func)
+ [![Build Status](https://travis-ci.com/freaktechnik/eslint-plugin-array-func.svg?branch=master)](https://travis-ci.com/freaktechnik/eslint-plugin-array-func) [![codecov](https://codecov.io/gh/freaktechnik/eslint-plugin-array-func/branch/master/graph/badge.svg)](https://codecov.io/gh/freaktechnik/eslint-plugin-array-func)
 
 Rules for Array functions and methods.