use the non-hash dependent Rack utils API

eventually we will refactor this to not know about header hashes

Gemfile.lock

@@ -27,7 +27,7 @@ GIT
 
 GIT
   remote: git://github.com/rack/rack.git
-  revision: c94e22401d4719b4d78378c7b63362cd692f9005
+  revision: fd20c3fa80128b19341ba8a0e0fae3bdc7c4c483
   specs:
     rack (2.0.0.alpha)
       json

actionpack/lib/action_dispatch/http/response.rb

@@ -257,11 +257,11 @@ def body_parts
     end
 
     def set_cookie(key, value)
-      ::Rack::Utils.set_cookie_header!(header, key, value)
+      header[SET_COOKIE] = ::Rack::Utils.add_cookie_to_header(header[SET_COOKIE], key, value)
     end
 
     def delete_cookie(key, value={})
-      ::Rack::Utils.delete_cookie_header!(header, key, value)
+      header[SET_COOKIE] = ::Rack::Utils.add_remove_cookie_to_header(header[SET_COOKIE], key, value)
     end
 
     # The location header we'll be responding with.