doc: Update Build Status badge

The previous URL no longer works and shows "no status".

Author: antoineco

README.md

@@ -1,7 +1,7 @@
 # Elastic stack (ELK) on Docker
 
 [![Elastic Stack version](https://img.shields.io/badge/Elastic%20Stack-7.17.28-00bfb3?style=flat&logo=elastic-stack)](https://www.elastic.co/blog/category/releases)
-[![Build Status](https://github.com/deviantony/docker-elk/workflows/CI/badge.svg?branch=release-7.x)](https://github.com/deviantony/docker-elk/actions?query=workflow%3ACI+branch%3Arelease-7.x)
+[![Build Status](https://github.com/deviantony/docker-elk/actions/workflows/ci.yml/badge.svg?branch=release-7.x)](https://github.com/deviantony/docker-elk/actions/workflows/ci.yml?query=branch%3Arelease-7.x)
 [![Join the chat](https://badges.gitter.im/Join%20Chat.svg)](https://app.gitter.im/#/room/#deviantony_docker-elk:gitter.im)
 
 Run the version 7.x of the [Elastic stack][elk-stack] with Docker and Docker Compose.