Improve Ruby example

doc/ci/quick_start/README.md

@@ -80,10 +80,11 @@ so you have to pay extra attention to indentation. Always use spaces, not tabs.
 Below is an example for a Ruby on Rails project:
 
 ```yaml
-image: "ruby:2.5"
-
-before_script:
-  - sudo apt-get update -qq && sudo apt-get install -y -qq sqlite3 libsqlite3-dev nodejs
+default:
+  image: ruby:2.5
+  before_script:
+    - apt-get update
+    - apt-get install -y sqlite3 libsqlite3-dev nodejs
     - ruby -v
     - which ruby
     - gem install bundler --no-document