Debian's ruby has the latest security patches applied

--- a/lib/system_check/app/ruby_version_check.rb
+++ b/lib/system_check/app/ruby_version_check.rb
@@ -7,7 +7,7 @@ module SystemCheck
       set_check_pass -> { "yes (#{self.current_version})" }
 
       def self.required_version
-        @required_version ||= Gitlab::VersionInfo.new(2, 5, 3)
+        @required_version ||= Gitlab::VersionInfo.new(2, 3, 3)
       end
 
       def self.current_version