Bump required Ruby version check to 2.5.3

Relates to https://gitlab.com/gitlab-org/gitlab-ce/issues/58079

Closes https://gitlab.com/gitlab-org/gitlab-ce/issues/60704

changelogs/unreleased/sh-bump-ruby-required-version-check.yml

+---
+title: Bump required Ruby version check to 2.5.3
+merge_request: 27495
+author:
+type: other

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, 3, 5)
+        @required_version ||= Gitlab::VersionInfo.new(2, 5, 3)
       end
 
       def self.current_version