Update dependency-injection.md

Author: locks

guides/v3.5.0/applications/dependency-injection.md

@@ -247,8 +247,10 @@ export default Component.extend({
     if (!this.song) {
       return null;
     }
+
     let applicationInstance = getOwner(this);
     let audioType = this.song.audioType;
+
     return applicationInstance.lookup(`service:audio-${audioType}`);
   }),