Merge branch 'master' into 'master'

docs: Correct YAML indentation

See merge request gitlab-org/gitlab-ce!21631

doc/ci/docker/using_docker_build.md

@@ -456,13 +456,13 @@ an application-specific deploy script:
 ```yaml
 image: docker:stable
 services:
-- docker:dind
+  - docker:dind
 
 stages:
-- build
-- test
-- release
-- deploy
+  - build
+  - test
+  - release
+  - deploy
 
 variables:
   DOCKER_HOST: tcp://docker:2375