Upgrade Ruby to 2.3.5

Part of gitlab-org/gitlab-ce#38040

.gitlab-ci.yml

-image: "dev.gitlab.org:5005/gitlab/gitlab-build-images:ruby-2.3.3-golang-1.8-git-2.13-phantomjs-2.1-node-8.x-yarn-1.0-postgresql-9.6"
+image: "dev.gitlab.org:5005/gitlab/gitlab-build-images:ruby-2.3.5-golang-1.8-git-2.13-phantomjs-2.1-node-8.x-yarn-1.0-postgresql-9.6"
 
 .default-cache: &default-cache
-  key: "ruby-233-with-yarn"
+  key: "ruby-235-with-yarn"
   paths:
     - vendor/ruby
     - .yarn-cache/
@@ -551,7 +551,7 @@ karma:
   <<: *dedicated-runner
   <<: *except-docs
   <<: *pull-cache
-  image: "dev.gitlab.org:5005/gitlab/gitlab-build-images:ruby-2.3.3-golang-1.8-git-2.13-chrome-61.0-node-8.x-yarn-1.0-postgresql-9.6"
+  image: "dev.gitlab.org:5005/gitlab/gitlab-build-images:ruby-2.3.5-golang-1.8-git-2.13-chrome-61.0-node-8.x-yarn-1.0-postgresql-9.6"
   stage: test
   variables:
     BABEL_ENV: "coverage"

.ruby-version

-2.3.3
+2.3.5

changelogs/unreleased/zj-ruby-2-3-5.yml

+---
+title: Upgrade Ruby to 2.3.5 to include security patches
+merge_request: 15099
+author:
+type: security

lib/system_check/app/ruby_version_check.rb

@@ -5,7 +5,7 @@ module SystemCheck
       set_check_pass -> { "yes (#{self.current_version})" }
 
       def self.required_version
-        @required_version ||= Gitlab::VersionInfo.new(2, 3, 3)
+        @required_version ||= Gitlab::VersionInfo.new(2, 3, 5)
       end
 
       def self.current_version