Remove useless conditional

If the response method is defined, then calling `response` will return a
response.

actionpack/lib/abstract_controller/rendering.rb

@@ -118,7 +118,7 @@ def _set_content_type(type) # :nodoc:
     def _normalize_render(*args, &block)
       options = _normalize_args(*args, &block)
       #TODO: remove defined? when we restore AP <=> AV dependency
-      if defined?(request) && request && request.variant.present?
+      if defined?(request) && request.variant.present?
         options[:variant] = request.variant
       end
       _normalize_options(options)