[docs] Updated status badge in README

[skip ci]

(cherry picked from commit 671eba3)

Author: nemesifier

README.rst

@@ -1,8 +1,8 @@
 Docker-OpenWISP
 ===============
 
-.. image:: https://github.com/openwisp/docker-openwisp/workflows/Automation%20Tests/badge.svg
-    :target: https://github.com/openwisp/docker-openwisp/actions?query=workflow%3A%22Automation+Tests%22
+.. image:: https://github.com/openwisp/docker-openwisp/actions/workflows/ci.yml/badge.svg
+    :target: https://github.com/openwisp/docker-openwisp/actions/workflows/ci.yml
 
 .. image:: https://img.shields.io/badge/registry-openwisp-blue.svg
     :target: https://gitlab.com/openwisp/docker-openwisp/container_registry