Remove Ruby 2.5.3
Remove Ruby 2.5.3

Nothing is using it according to `fab [aws_]production
puppet_class:govuk_rbenv::all rbenv.version_in_use:2.5.3`.

alphagov/govuk-puppet,alphagov/govuk-puppet,alphagov/govuk-puppet,alphagov/govuk-puppet,alphagov/govuk-puppet,alphagov/govuk-puppet