Remove unnecessary env variable for specifying graphql version

Author: khamusa

Gemfile

@@ -4,11 +4,3 @@ source 'https://rubygems.org'
 
 # Specify your gem's dependencies in rspec-graphql_matchers.gemspec
 gemspec
-
-# rubocop:disable Bundle/DuplicatedGem
-if ENV['GRAPHQL_GEM_VERSION'] == '1.8'
-  gem 'graphql', '~> 1.8.0'
-elsif ENV['GRAPHQL_GEM_VERSION'] == '1.9'
-  gem 'graphql', '~> 1.9.0'
-end
-# rubocop:enable Bundle/DuplicatedGem