Merge pull request rails#38991 from eugeneius/actionpack_minimum_rack_version

Update minimum Rack version to 2.0.9

Author: eugeneius

actionpack/actionpack.gemspec

@@ -34,7 +34,7 @@ Gem::Specification.new do |s|
 
   s.add_dependency "activesupport", version
 
-  s.add_dependency "rack",      "~> 2.0", ">= 2.0.8"
+  s.add_dependency "rack",      "~> 2.0", ">= 2.0.9"
   s.add_dependency "rack-test", ">= 0.6.3"
   s.add_dependency "rails-html-sanitizer", "~> 1.0", ">= 1.2.0"
   s.add_dependency "rails-dom-testing", "~> 2.0"