remove obsolete init image, bump dashboard version 1.8.1 -> 1.8.3

roles/kubernetes-apps/ansible/defaults/main.yml

@@ -41,9 +41,7 @@ netchecker_server_memory_requests: 64M
 # Dashboard
 dashboard_enabled: true
 dashboard_image_repo: gcr.io/google_containers/kubernetes-dashboard-amd64
-dashboard_image_tag: v1.8.1
-dashboard_init_image_repo: gcr.io/google_containers/kubernetes-dashboard-init-amd64
-dashboard_init_image_tag: v1.0.1
+dashboard_image_tag: v1.8.3
 
 # Limits for dashboard
 dashboard_cpu_limit: 100m