Adapt README.md to new action.

Author: VolkerHartmann

README.md

@@ -1,6 +1,6 @@
 # Indexing-service
 
-[![Build Status](https://travis-ci.com/kit-data-manager/indexing-service.svg?branch=master)](https://travis-ci.com/kit-data-manager/indexing-service)
+![GitHub](../../actions/workflows/gradle.yml/badge.svg)
 [![Coverage Status](https://coveralls.io/repos/github/kit-data-manager/indexing-service/badge.svg?branch=master)](https://coveralls.io/github/kit-data-manager/indexing-service?branch=master)
 ![License](https://img.shields.io/github/license/kit-data-manager/indexing-service.svg)