fix rubocop issues (#4875)

Author: johha

docs/v3/Gemfile

@@ -1,9 +1,9 @@
 source 'https://rubygems.org'
 
+gem 'autoprefixer-rails', '~> 10.4.7'
 gem 'json', '>= 2.3.0'
 gem 'middleman', '~> 4.6'
 gem 'middleman-autoprefixer', '~> 3.0', '>= 3.0.0'
-gem 'autoprefixer-rails', '~> 10.4.7'
 gem 'middleman-gh-pages', '>= 0.0.3'
 gem 'middleman-livereload', '>= 3.4.7'
 gem 'middleman-syntax', '~> 3.6'