Adapt build status icon for ci.jenkins.io permissions change (#2831)

Author: MarkEWaite

README.md

@@ -1,6 +1,6 @@
 # Jenkins Configuration as Code (a.k.a. JCasC) Plugin
 
-[![Build Status](https://ci.jenkins.io/job/Plugins/job/configuration-as-code-plugin/job/master/badge/icon)](https://ci.jenkins.io/job/Plugins/job/configuration-as-code-plugin/job/master/)
+[![Build Status](https://ci.jenkins.io/buildStatus/icon?job=Plugins%2Fconfiguration-as-code-plugin%2Fmaster)](https://ci.jenkins.io/job/Plugins/job/configuration-as-code-plugin/job/master/)
 [![Contributors](https://img.shields.io/github/contributors/jenkinsci/configuration-as-code-plugin.svg)](https://github.com/jenkinsci/configuration-as-code-plugin/graphs/contributors)
 [![Jenkins Plugin](https://img.shields.io/jenkins/plugin/v/configuration-as-code.svg)](https://plugins.jenkins.io/configuration-as-code)
 [![GitHub release](https://img.shields.io/github/release/jenkinsci/configuration-as-code-plugin.svg?label=changelog)](https://github.com/jenkinsci/configuration-as-code-plugin/releases/latest)