Remove unnecessary hack

Author: pirj

Gemfile-rails-dependencies

@@ -1,10 +1,5 @@
 version_file = File.expand_path("../.rails-version", __FILE__)
 
-# FIXME: rack 2.1.0 introduces a deprecation warning that rails is triggering,
-# but in later versions this warning will be removed. Get rid of this hack once
-# rack 2.1.0+ is out.
-gem 'rack', '!= 2.1.0'
-
 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"