Remove duplicate ostruct entry from Gemfile (#2212)

Author: larouxn

Gemfile

@@ -25,7 +25,6 @@ group :development do
 
   gem 'rubocop', '~> 1.0', '<= 1.11'
   gem 'rubocop-performance'
-  gem 'ostruct'
 
   # docs
   gem 'github-markup'