Remove explicit arel dependency

Arel was swallowed by Rails back in 2018

Author: pirj

Gemfile-rails-dependencies

@@ -3,7 +3,6 @@ version_file = File.expand_path("../.rails-version", __FILE__)
 case version = ENV['RAILS_VERSION'] || (File.exist?(version_file) && File.read(version_file).chomp) || ''
 when /master/
   gem "rails", :git => "https://github.com/rails/rails.git"
-  gem "arel", :git => "https://github.com/rails/arel.git"
   gem "journey", :git => "https://github.com/rails/journey.git"
   gem "activerecord-deprecated_finders", :git => "https://github.com/rails/activerecord-deprecated_finders.git"
   gem "web-console", :git => "https://github.com/rails/web-console", :group => :development