Update the example config so that it works

`labels` -> `external_labels`
`target_groups` -> `static_configs`

Author: ivanychev

examples/prometheus/prometheus.yml

@@ -2,13 +2,13 @@ global:
   scrape_interval: 10s
   evaluation_interval: 10s
 
-  labels:
+  external_labels:
     monitor: django-monitor
 
 rule_files:
 - "django.rules"
 
 scrape_configs:
 - job_name: "django"
-  target_groups:
-  - targets: ["localhost:8000"]	
+  static_configs:
+  - targets: ["localhost:8000"]