Use own ruby image for production CI

.gitlab-ci.yml

@@ -55,7 +55,7 @@ stop-review:
     - master
 
 production:
-  image: debian:stretch
+  image: 0xacab.org:4567/leap/docker/ruby:stretch_amd64
   stage: production
   environment:
     name: production
@@ -74,4 +74,3 @@ production:
     - apt-get update
     - apt-get install -y --no-install-recommends capistrano
     - cap deploy
-