Fix typo

Author: tmilewski

Gemfile

@@ -9,7 +9,7 @@ group :test do
   gem "rack-test"
   gem "rest-client", "~> 1.7.3", :platforms => %i[jruby ruby_18]
   gem "rspec", "~> 3.2"
-  gem "rubocop", ">= 0.51", :platforms => %i[ruby_19 ruby_20 ruby_21 ruby_22, :ruby_23, :ruby_24]
+  gem "rubocop", ">= 0.51", :platforms => %i[ruby_19 ruby_20 ruby_21 ruby_22 ruby_23 ruby_24]
   gem "simplecov", ">= 0.9"
   gem "webmock", "~> 1.0"
   gem "addressable", "~> 2.3.8", :platforms => [:jruby, :ruby_18]