Remove ruby-next from dev dependecies

Author: DmitryTsepelev

graphql-ruby-fragment_cache.gemspec

@@ -30,7 +30,6 @@ Gem::Specification.new do |spec|
   spec.add_development_dependency "rake", ">= 13.0"
   spec.add_development_dependency "rspec", "~> 3.9"
   spec.add_development_dependency "timecop"
-  spec.add_development_dependency "ruby-next", ">= 0.10"
   spec.add_development_dependency "unparser", "0.6.0"
   spec.add_development_dependency "graphql-batch"
   spec.add_development_dependency "parser"