Removes link to deprecated docker image build

packaging/docker/README.md

 # Grafana Docker image
 
-[![CircleCI](https://circleci.com/gh/grafana/grafana-docker.svg?style=svg)](https://circleci.com/gh/grafana/grafana-docker)
-
 ## Running your Grafana container
 
 Start your container binding the external port `3000`.
@@ -42,4 +40,4 @@ Further documentation can be found at http://docs.grafana.org/installation/docke
 * Plugins dir (`/var/lib/grafana/plugins`) is no longer a separate volume
 
 ### v3.1.1
-* Make it possible to install specific plugin version https://github.com/grafana/grafana-docker/issues/59#issuecomment-260584026
\ No newline at end of file
+* Make it possible to install specific plugin version https://github.com/grafana/grafana-docker/issues/59#issuecomment-260584026