Remove variables not available in prometheus 2.0

Closes-Bug: PROD-16609
Change-Id: I4865b92fa1ca46e3c8d5e1bbbb5855aff337726f
diff --git a/prometheus/server/init.yml b/prometheus/server/init.yml
index 99fdceb..5d115ac 100644
--- a/prometheus/server/init.yml
+++ b/prometheus/server/init.yml
@@ -4,6 +4,7 @@
     prometheus_server_data_directory: /data
   prometheus:
     server:
+      version: 2.0
       dir:
         data: /srv/volumes/local/prometheus/data
         config: /srv/volumes/local/prometheus/config