chore(readme): remove Greenkeeper badge (#43)

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

README.md

@@ -1,7 +1,7 @@
 [![npm version](https://badge.fury.io/js/puml2code.svg)](https://badge.fury.io/js/puml2code)
 [![CircleCI](https://circleci.com/gh/jupe/puml2code/tree/master.svg?style=svg)](https://circleci.com/gh/jupe/puml2code/tree/master)
 [![JavaScript Style Guide](https://img.shields.io/badge/code_style-standard-brightgreen.svg)](https://standardjs.com)
-[![License badge](https://img.shields.io/badge/license-MIT-blue.svg)](https://img.shields.io) [![Greenkeeper badge](https://badges.greenkeeper.io/jupe/puml2code.svg)](https://greenkeeper.io/)
+[![License badge](https://img.shields.io/badge/license-MIT-blue.svg)](https://img.shields.io) 
 
 
 ## PlantUML code generator (puml2code)