Use released arel

Gemfile

@@ -14,7 +14,6 @@ gem 'rack-cache', '~> 1.2'
 gem 'jquery-rails', '~> 4.0.0.beta2'
 gem 'coffee-rails', '~> 4.1.0'
 gem 'turbolinks'
-gem 'arel', github: 'rails/arel'
 
 # require: false so bcrypt is loaded only when has_secure_password is used.
 # This is to avoid ActiveModel (and by extension the entire framework)

activerecord/activerecord.gemspec

@@ -24,5 +24,5 @@
   s.add_dependency 'activesupport', version
   s.add_dependency 'activemodel',   version
 
-  s.add_dependency 'arel', '>= 6.0.0.beta2', '< 6.1'
+  s.add_dependency 'arel', '~> 6.0'
 end