Merge branch '195165-replace-eol-ruby-versions-docs-v2-docs' into 'master'

Replace Ruby 2.1/2.2/2.3 with Ruby latest

Closes #195165

See merge request gitlab-org/gitlab!27268

doc/ci/docker/using_docker_images.md

@@ -489,7 +489,7 @@ Look for the `[runners.docker]` section:
 
 ```toml
 [runners.docker]
-  image = "ruby:2.1"
+  image = "ruby:latest"
   services = ["mysql:latest", "postgres:latest"]
 ```