Fix dependency issue for 6.x

Author: picandocodigo

elasticsearch-api/elasticsearch-api.gemspec

@@ -58,7 +58,7 @@ Gem::Specification.new do |s|
   end
 
   if defined?(RUBY_VERSION) && RUBY_VERSION > '1.9'
-    s.add_development_dependency "ruby-prof" unless defined?(JRUBY_VERSION) || defined?(Rubinius)
+    s.add_development_dependency "ruby-prof" unless defined?(JRUBY_VERSION) || defined?(Rubinius) || RUBY_VERSION < '2.4'
     s.add_development_dependency "jbuilder"
     s.add_development_dependency "escape_utils" unless defined? JRUBY_VERSION
     s.add_development_dependency "simplecov", '~> 0.17', '< 0.18'