chore(readme): remove Greenkeeper badge (#9)

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

README.md

@@ -13,7 +13,7 @@ governing permissions and limitations under the License.
 [![Version](https://img.shields.io/npm/v/@adobe/aio-lib-events.svg)](https://npmjs.org/package/@adobe/aio-lib-events)
 [![Downloads/week](https://img.shields.io/npm/dw/@adobe/aio-lib-events.svg)](https://npmjs.org/package/@adobe/aio-lib-events)
 [![Build Status](https://travis-ci.com/adobe/aio-lib-events.svg?branch=master)](https://travis-ci.com/adobe/aio-lib-events)
-[![License](https://img.shields.io/badge/License-Apache%202.0-blue.svg)](https://opensource.org/licenses/Apache-2.0) [![Greenkeeper badge](https://badges.greenkeeper.io/adobe/aio-lib-events.svg)](https://greenkeeper.io/)
+[![License](https://img.shields.io/badge/License-Apache%202.0-blue.svg)](https://opensource.org/licenses/Apache-2.0) 
 [![Codecov Coverage](https://img.shields.io/codecov/c/github/adobe/aio-lib-events/master.svg?style=flat-square)](https://codecov.io/gh/adobe/aio-lib-events/)
 
 # Adobe I/O Events Lib